Import protected Mail Merge Document

ppn

Via the style sheet tool (v2) we import a mail merge document. Part(s) of this document is protected. We just want to add merge fields to the document. Users are not allowed to change the protected parts. Import works fine but when we want to open the mail merge document we run into an error (The call to member OpenDataSource failed) due to the protection. I can unprotect the document so it can be opened for mailmerge but how do I put the protection back on again? So when the resulting style sheet is called from customercard the user can see the result but not change things in the originally protected areas?