VBA - Is it possible to have an error message that automatically pops-up based on condition? - excel

Question

If the users fill in the serial no. column in col B (it doesn't have to be all 10 of them, as long as one is filled), they need to fill up the other columns from col C to col F. Hence, if col B is filled up but any of the cells in col C to F are not filled up, I want an error message to pop up. I hope the image below gives a clearer idea..:
I'm not sure if Worksheet_SelectionChange will do what I want to accomplish...because I don't want to include a command button. As some users may not bother clicking on the command button to verify their inputs. This is the code I have at the moment, please feel free to advise accordingly....thank you:)
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Range("B4").Value = "" Then
MsgBox "serial no. is a Mandatory field", vbExclamation, "Required Entry"
Range("B4").Select
End If
If Range("B4:B") <> "" Then
If Range("C4:C").Value = "" Then
MsgBox "Product is a Mandatory field", vbExclamation, "Required Entry"
Range("C4:C").Select
End If
' Adding values from sheet 2 for fruits drop-down list.
If Not Intersect(Target, Range("D3")) Is Nothing Then
Sheets("Sheet1").Range("D3") = "[Please Select]"
Dim col As New Collection
Dim rng As Range
Dim i As Long
Dim dvlist As String
'Loop thru the data range
For Each rng In Sheet2.Range("B2:B7")
'ignore blanks
If Len(Trim(rng.Value)) <> 0 Then
'create a unique list
On Error Resume Next
col.Add rng.Value, CStr(rng.Value)
On Error GoTo 0
End If
Next rng
'concatenate with "," as the delimiter
For i = 2 To col.Count
dvlist = dvlist & col.Item(i) & ","
Next i
With Sheet1.Range("C2:C").Validation
.Delete
.Add Type:=xlValidateList, _
AlertStyle:=xlValidAlertStop, _
Formula1:=dvlist
End With
End If
' Adding values from sheet 2 for country of origin drop-down list.
If Not Intersect(Target, Range("E4")) Is Nothing Then
Sheets("Screening Request").Range("E4") = "[Please Select]"
'Loop thru the data range
For Each rng In Sheet2.Range("A2:A7")
'ignore blanks
If Len(Trim(rng.Value)) <> 0 Then
'create a unique list
On Error Resume Next
col.Add rng.Value, CStr(rng.Value)
On Error GoTo 0
End If
Next rng
'concatenate with "," as the delimiter for list in Sheet 2
For i = 2 To col.Count
dvlist1 = dvlist1 & col.Item(i) & ","
Next i
'add it to the DV
With Sheet1.Range("D3").Validation
.Delete
.Add Type:=xlValidateList, _
AlertStyle:=xlValidAlertStop, _
Formula1:=dvlist1
End With
End If
' This is for the date (YYYYMMDD) column. I need it to be in YYYYMMDD format:
If Not Intersect(Target, Range("F4:F13")) Is Nothing Then
If Not IsNumeric(.Value) And Not cel.NumberFormat = "yyyymmdd" Then
MsgBox "Date format must be in YYYYMMDD"
cel.Value = ""
Exit Sub
Else: cel.NumberFormat = "yyyymmdd"
End If
End With
End If

Answer 1

In general, you are making life much too hard for yourself. Use the tools that Excel provides (and there are many); you do not need to re-invent the wheel.
For example the lists for fruits and country of origin in your Sheet2 should be used as a list for data validation purposes in Sheet1 (Data Tab, Data Tools, Data Validation). Choose Allow List, make sure Ignore blank and In-cell dropdown are checked and select the range from Sheet2.
Similarly you can use data validation to validate dates in your last column.
You now do not need to validate these columns yourself, as they will always have blanks or valid values.
Combine this with my suggestion of conditional formatting (eg for the range c4:c13 you should enter =AND(B4<>"",ISBLANK(C4)) and for all three columns, you can produce a very simple verification routine. Something like:
Private Sub Workbook_BeforeClose(Cancel As Boolean)
Cancel = MissingEntries()
End Sub
Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Cancel = MissingEntries()
End Sub
Private Function MissingEntries() As Boolean
Dim i As Integer
Dim j As Integer
Dim atLeastOneLine As Boolean
atLeastOneLine = False
For i = 4 To 13
If (Cells(i, 2) <> "") Then
atLeastOneLine = True
For j = 3 To 6
If Cells(i, j) = "" Then
MsgBox ("Please supply values for highlighted cells")
MissingEntries = True
Exit Function
End If
Next
If WrongSerialNumber(i) Then
MissingEntries = True
Exit Function
End If
End If
Next
If Not atLeastOneLine Then
MsgBox ("Please supply values for at least one line")
MissingEntries = True
Else
MissingEntries = False
End If
End Function
Private Function WrongSerialNumber(i As Integer) As Boolean
Dim yr As Integer
Dim serialNo As String
Dim yrStr As String
Dim yrCell As String
serialNo = Cells(i, 2)
If Len(serialNo) < 3 Then
WrongSerialNumber = True
MsgBox "Serial Number for row no. " + CStr(i - 3) + " is too short. Please correct."
Exit Function
End If
yrCell = Cells(i, 6)
If Len(yrCell) = 8 Then
yr = CInt(Left(Cells(i, 6), 4))
If yr > 1968 Then
If Mid(yrCell, 3, 2) <> Mid(serialNo, 2, 2) Then
WrongSerialNumber = True
MsgBox "Serial Number for row no. " + CStr(i - 3) + " has wrong second and third digits. These should match the third and fourth digits of the date. Please correct."
Exit Function
End If
End If
End If
WrongSerialNumber = False
End Function
Note that I validate on both close and save. The former is optional.
Because of the highlighting, a simple message suffices, you are spared the work of informing the user, which cells are missing. In this way the combination of in-built Data Validation and Conditional Formatting makes the remainder of your task so much easier.