Digital Signature Removal

[Dan]

I have an InfoPath 2007 form on a SharePoint 2007 site and after users enter
in the required information, I digitally sign it to lock the data the users
entered. The form is opened in a Browser by default.

However once I sign it and the data is locked, any other user can log into
SharePoint and hit the remove button next to my signature and remove it and
edit the form.

Is there any way to keep other users from removing my signature from an
InfoPath form on a SharePoint site opened within Explorer.

Thanks
Dan