automatically declare object class variable when creating new sheet in EXCEL - excel

Question

How do I declare a - private - class variable, when a new sheet is created using the tab. It has to be done automatically. I presume it is a good idea to declare it by using the
Private Sub Workbook_NewSheet(ByVal Sh As Object) -event from the Wookbook object
Sub Workbook_NewSheet(ByVal Sh As Object)
Dim sh.privateVariableOfSheet As Integer
Declare New sh.privateVariableOfSheet2 As Integer
End Sub
Both above 'declarations' fails of course!
And for the completeness, how to refer to this variable from an ordinary module.

Answer 1

Another method is to use the CustomProperties collection of the Worksheet. For example:
Option Explicit
Private Sub Workbook_NewSheet(ByVal Sh As Object)
Sh.CustomProperties.Add Name:=Sh.Name, Value:=99
End Sub
You can then use it later in a sub-routine:
Option Explicit
Sub Test()
Dim var As Variant
var = ThisWorkbook.Worksheets("Sheet13").CustomProperties(1)
MsgBox var
End Sub

Answer 2

Let take some class - clsFoo - which has a single property of type Range with a getter and setter:
Private m_rngSomewhere As Range
Public Property Get SomeRange() As Range
Set SomeRange = m_rngSomewhere
End Property
Public Property Set SomeRange(rng As Range)
Set m_rngSomewhere = rng
End Property
Now, in the Workbook code module you have:
a Public variable which we will set as a Dictionary
a Sub to instantiate the Dictionary - could be called from Workbook_Open or something
an event handler for Workbook_NewSheet
The event handler creates a new instance of clsFoo and sets its property as a Range from the new Worksheet, and then adds that to the dictionary (and checks if it was already there for some new reason).
Code in Workbook module:
Option Explicit
Public SheetFooDic As Object
Public Sub InitialiseSheetFooDic()
Set SheetFooDic = CreateObject("Scripting.Dictionary")
End Sub
Private Sub Workbook_NewSheet(ByVal Sh As Object)
Dim rng As Range
Dim cls As clsFoo
If Not SheetFooDic.Exists(Sh) Then
Set rng = Sh.Range("A1")
Set cls = New clsFoo
Set cls.SomeRange = rng
SheetFooDic.Add Sh, cls
End If
End Sub
This leaves you needing to simply use some Worksheet object as a key into the Dictionary in order to retrieve the Range you stored when the Worksheet was created. You can refer to the public Dictionary like this:
ThisWorkbook.SheetFooDic(ThisWorkbook.Worksheets("Sheet2")).SomeRange.Address
And get:
$A$1

Answer 3

You can store the address of the last selected cell as a string. So, asking for an object variable might be misleading. Either way, the easiest way is to declare a public variable (for example PrevCell As String, or As Range if you prefer or need the value) in each of your worksheets' code and set that variable in each sheet's Selection_Change event procedure.
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
PrevCell = Target.Cells(1) ' or .Address
End Sub
Since you may find it useful to avoid recording selections of multiple cells my above procedure just records the address of the first cell which avoid errors that often crop up when a copy/paste action was performed on a sheet.
Now, when you insert a new sheet, don't use the Add method. Instead copy an existing sheet and clean it up the way you want. In this way the new sheet will already have the variable and the code that sets it.
I can't imagine your having need of the previous cell in any circumstance other than when the sheet is activated, but if my imagination is insufficient in this case, you might declare a global array with an element for each sheet, using the sheets' CodeName property for identification. This array would be set by the Selection_Change event procedure as demonstrated above, but when a sheet which isn't known to the array tries to register its latest selection it must be a new sheet and the array is extended to include it. The code to do so is inherited from other sheets by the same method described above.