OK, so I think I might have figured it out...

I added the following code to the "Activate Sheet" command in the "Workbook" module:

Private Sub Workbook_SheetActivate(ByVal Sh As Object)
ActiveSheet.Protect userinterfaceOnly:=True
End Sub
I've not fully tested it thoroughly, but from a quick testing, it seems to be working.

I wanted to post this in case anyone else is having a similar issue, that way it may help them as well.

If this works 100% of the time after I'm done testing, I'll mark my own question as "solved" by my own solution - I wonder if I can give myself Reputation??