|Enter something directly in the cell that shows the "extra dates".|
I'm guessing that if it is a hidden formula you will overwrite it.
If it's a macro, it'll go back doing whatever the macro tells it to do.
Maybe that will point us in the right direction.
Macros can be hidden and protected so you may not be able to find it (easily).
Click Here Before Posting Data or VBA Code ---> How To Post Data or Code.