Excel VBA how to link a class and a control? - excel

Question

I am using Excel 2003 with VBA, I am dynamically creating check box controls on a sheet and want to link the VBA controls to a class so that when a user clicks on a checkbox an event is fired so I can do something.
From what I've read it would seem that creating a user class is the solution, but having tried this I can't get it to work.
My user class looks like this:
Option Explicit
Public WithEvents cbBox As MSForms.checkbox
Private Sub cbBox_Change()
MsgBox "_CHANGE"
End Sub
Private Sub cbBox_Click()
MsgBox "_CLICK"
End Sub
My code to create the checkboxes:
For Each varExisting In objColumns
'Insert the field name
objColumnHeadings.Cells(lngRow, 1).Value = varExisting
'Insert a checkbox to allow selection of the column
Set objCell = objColumnHeadings.Cells(lngRow, 2)
Dim objCBclass As clsCheckbox
Set objCBclass = New clsCheckbox
Set objCBclass.cbBox = ActiveSheet.OLEObjects.Add( _
ClassType:="Forms.CheckBox.1" _
, Left:=300 _
, Top:=(objCell.Top + 2) _
, Height:=10 _
, Width:=9.6).Object
objCBclass.cbBox.Name = "chkbx" & lngRow
objCBclass.cbBox.Caption = ""
objCBclass.cbBox.BackColor = &H808080
objCBclass.cbBox.BackStyle = 0
objCBclass.cbBox.ForeColor = &H808080
objCheckboxes.Add objCBclass
lngRow = lngRow + 1
Next
The checkboxes are visible in the sheet, but when I click on them, no message box is displayed so the link to the class doesn't seem to be working.
Why?
Edit...If after adding the checkboxes I go into the VB IDE and select one of the created checkboxes from the list of controls, then select Click from the Procedure drop down list, it will insert the code for a call back which if I add a message box to this, works when I click on the same checkbox...so how can I achieve this in code? I've tried recording a macro to do this, nothing was recorded.

Answer 1

Edit by S.Platten, jump to the bottom for how this helped me fix the problem...
Due to some weird reason, VBA doesn't hook up the events for Sheet's ActiveX control in the same execution cycle in which they were added. So, we need to come out of the cycle which added the controls and then invoke the event adding proc in next cycle. Application.OnTime helps here.
Its seems a bit of overkill but it works :)
Option Explicit
Dim collChk As Collection
Dim timerTime
Sub master()
'/ Add the CheckBoxes First
Call addControls
'<< Due to some weird reason, VBA doesn't hook up the events for Sheet's ActiveX control in the same
'execution cycle in which they were added. So, we need to come out of the cycle which added the controls
'and then invoke the event adding proc in next cycle. >>
'/ Start Timer. Timer will call the sub to add the events
Call StartTimer
End Sub
Sub addControls()
Dim ctrlChkBox As MSForms.CheckBox
Dim objCell As Range
Dim i As Long
'Intialize the collection to hold the classes
Set collChk = New Collection
'/ Here Controls are added. No Events, yet.
For i = 1 To 10
Set objCell = Sheet1.Cells(i, 1)
Set ctrlChkBox = Sheet1.OLEObjects.Add( _
ClassType:="Forms.CheckBox.1" _
, Left:=1 _
, Top:=(objCell.Top + 2) _
, Height:=objCell.Height _
, Width:=100).Object
ctrlChkBox.Name = "chkbx" & objCell.Row
Next
End Sub
Sub addEvents()
Dim ctrlChkBox As MSForms.CheckBox
Dim objCBclass As clsCheckBox
Dim x As Object
'Intialize the collection to hold the classes
Set collChk = New Collection
'/ Here we assign the event handler
For Each x In Sheet1.OLEObjects
If x.OLEType = 2 Then
Set ctrlChkBox = x.Object
Set objCBclass = New clsCheckBox
Set objCBclass.cbBox = ctrlChkBox
collChk.Add objCBclass
Debug.Print x.Name
End If
Next
'/ Kill the timer
Call StopTimer
End Sub
Sub StartTimer()
timerTime = Now + TimeSerial(0, 0, 1)
Application.OnTime EarliestTime:=timerTime, Procedure:="addEvents", _
Schedule:=True
End Sub
Sub StopTimer()
On Error Resume Next
Application.OnTime EarliestTime:=timerTime, Procedure:="addEvents", _
Schedule:=False
End Sub
Class Module: clsCheckBox
Option Explicit
Public WithEvents cbBox As MSForms.CheckBox
Private Sub cbBox_Change()
MsgBox "_CHANGE"
End Sub
Private Sub cbBox_Click()
MsgBox "_CLICK"
End Sub
Edit continued...
The class (clsCheckbox):
Option Explicit
Public WithEvents cbBox As MSForms.checkbox
Private Sub cbBox_Click()
MsgBox "_CLICK"
End Sub
Module1
Public objCheckboxes As Collection
Public tmrTimer
Public Sub addEvents()
Dim objCheckbox As clsCheckbox
Dim objMSCheckbox As Object
Dim objControl As Object
Set objCheckboxes = New Collection
For Each objControl In Sheet1.OLEObjects
If objControl.OLEType = 2 _
And objControl.progID = "Forms.CheckBox.1" Then
Set objMSCheckbox = objControl.Object
Set objCheckbox = New clsCheckbox
Set objCheckbox.cbBox = objMSCheckbox
objCheckboxes.Add objCheckbox
End If
Next
Call stopTimer
End Sub
Public Sub startTimer()
tmrTimer = Now + TimeSerial(0, 0, 1)
Application.OnTime EarliestTime:=tmrTimer _
, Procedure:="addEvents" _
, Schedule:=True
End Sub
Public Sub stopTimer()
On Error Resume Next
Application.OnTime EarliestTime:=tmrTimer _
, Procedure:="addEvents" _
, Schedule:=False
End Sub
The code in the sheet that adds the controls:
Dim objControl As MSForms.checkbox
For Each varExisting In objColumns
'Insert the field name
objColumnHeadings.Cells(lngRow, 1).Value = varExisting
'Insert a checkbox to allow selection of the column
Set objCell = objColumnHeadings.Cells(lngRow, 2)
Set objControl = ActiveSheet.OLEObjects.Add( _
ClassType:="Forms.CheckBox.1" _
, Left:=300 _
, Top:=(objCell.Top + 2) _
, Height:=10 _
, Width:=9.6).Object
objControl.Name = "chkbx" & lngRow
objControl.Caption = ""
objControl.BackColor = &H808080
objControl.BackStyle = 0
objControl.ForeColor = &H808080
lngRow = lngRow + 1
Next
This isn't the entire project, but enough to demonstrate the workings.

Answer 2

You are currently using ActiveX controls. Yet, ActiveX controls are bound to specific naming conventions. For example: if you insert an ActiveX button onto a sheet and name it btnMyButton then the sub must be named btnMyButton_Click. The same applies to checkboxes. If you insert a new checkbox with the name CheckBox2 then the sub's name must be CheckBox2_Click. In short, there cannot be a sub with the name cbBox_Change associated to any ActiveX checkbox.
So, what you really need (with ActiveX controls) is a way to change the VBA code on a sheet. But thus far I have never come across any such code (VBA code to change VBA code on a sheet).
A much easier route would be if you'd be willing to use form controls instead.
The following sub will create a (form control) checkbox and assign the macro tmpSO to it. The sub tmpSO (unlike subs for ActiveX controls) does not need to reside on the sheet but can be in any module.
Sub Insert_CheckBox()
Dim chk As CheckBox
Set chk = ActiveSheet.CheckBoxes.Add(390.75, 216, 72, 72)
chk.OnAction = "tmpSO"
End Sub
Since a from control is calling the sub tmpSO you can use Application.Caller in that sub and thereby know which checkbox has been calling this sub.
Sub tmpSO()
Debug.Print Application.Caller
End Sub
This will return the name of the CheckBox. So, you can use this one sub for all of your checkboxes any dynamically handle them based on their names (possibly using a Case Select).
Here is another example for tmpSO:
Sub tmpSO()
With ThisWorkbook.Worksheets(1).CheckBoxes(Application.Caller)
MsgBox "The checkbox " & Application.Caller & Chr(10) & _
"is currently " & IIf(.Value = 1, "", "not") & " checked."
End With
End Sub