Welcome to the Board!
Probably best to use a Case statement, structured something like this here, if you want a different message for each sheet:
VBA Code:
Private Sub Workbook_SheetActivate(ByVal Sh As Object)
On Error Resume Next
Select Case Sh.Name
Case "Sheet1"
MsgBox "line1" & vbCrLf & "line2" & vbCrLf & "line3" & vbCrLf & "line4", vbInformation, "Created 02/09/2024"
Case "Sheet2"
MsgBox ...
Case "Sheet3"
MsgBox ...
...
End Select
End Sub
If the messages are similar and can be programmed, we may be able to simplify it a bit. We would just need to know more details about it.