Thank you Doug for a quick answer. I tried to do so, but when I debug the code, I get this error: (translated from Norwegian) “Run time error 4605, This method or property is not available because the document is not a main document for mail merging”. I am not an experienced user of macros, so I have probably done something wrong.
I have locked the document using the functionality for forms. The form is to be filled in manually after the merging, using text fields.  

Thanks