How to Bypass SheetChange() Event Conditionally

Is there anyway to trigger the SheetChange() event sometimes but not all the time?

I've been asked to detect the last modified time stamp on every sheet in a normally 50-sheet workbook for review and QC purposes. Basically, reviewers can see the last modified info and a separate informational sign-off time stamp to make sure nothing is modified after the sign-off time. I used the SheetChange() event in ThisWorkbook but soon realized that it would disable the Undo/Redo feature because each time that event is triggered the Undo stack will be cleared. Not having the Undo/Redo will make our users very mad.

I have a couple questions:

1. Is there anyway of detecting the last-modified-info without using the SheetChange() event?
2. If I have to use SheetChange() for this, is there anyway to bypass it under certain conditions? I'm thinking, until there is a sign-off done on the worksheet, I really don't care when it was last modified. So at least until that time my users can have that Undo feature available. The challenge is, I can't figure out how to do an "Application.EnableEvents = False" outside the SheetChange() event so it won't be triggered all the time.

Here is the code I used for SheetChange(), it places the last modified value in cell A1 of each sheet. Thank you for your time and help!!!

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
    
'Cell A1 on each sheet will show the last modified timestamp

    Application.EnableEvents = False
    
    Dim isctrl As Boolean: isctrl = False
    
    For i = 1 To Sh.CustomProperties.Count
        If Sh.CustomProperties.Item(i).Name = "BDOSign_ControlSheet" Then
            isctrl = True
            Exit For
        End If
    Next i
    
    If Not isctrl Then Sh.Range("A1") = Now()
    
    Application.EnableEvents = True
End Sub