Hi mcallahan2,
Thanks for posting in the community, according to your description, you can try the following VBA:
1. Save the workbook as *.XLSM
2. Press ALT+F11 to open VBA editor, enter the following event macro for each sheets:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Application.EnableEvents = False
Cells(Rows.Count, Columns.Count).Value = Now
Application.EnableEvents = True
End Sub
3. Select “ThisWorkbook” to insert a Module, enter the following code:
Public Function Updatee() As Date
Application.Volatile
Dim w As Worksheet
Set w = Application.Caller.Parent
Updatee = w.Cells(Rows.Count, Columns.Count).Value
End Function
4. Go back to your workbook, use the function: “=Updatee()” to insert last modified timestamp of the current sheet, you can modify the cell to change its date format.
Hope the above method can be helpful to you, pleas feel free to post back to let us know the result.
Best Regards,
Arck