Stop a user from opening Excel if the Add-in is not found
 

I am writing a Document action pane in C#. I would like to stop the user
from opening the workbook if the associated assembly is not found. When the
xls file is moved from the directory, you receive a warning that the assembly
was not found... However the user is still able to edit and resave the file
and copy it back into the directory with un-sensored modifications. Is this
possible?

Thank you