I have a workbook containing a VB Project with a macro that adds a
reference to a dll if this reference is not yet there. The VB Project
is signed.
Now the problem is if somebody else runs this macro and saves the
workbook the following error message is displayed:
"You have modified a signed project. You do not have the correct key to
sign this project. The signature will be discarded."
Obviously excel consideres adding a reference as changing the VB
Project and tries to save this change.

Is there a way to "discard the change" and prevent the VB Project from
being saved again, so the signature won't disappear?

Alternatively, is there a way to add the reference without changing the
VB Project?