External Macro Links - how to make internal

I am creating new files from an existing excel file using VBA. The new files contain macros assigned to buttons. To get the macros into the new files, I am exporting and then importing them. I then email the file to another user. All this is done ~150 times by a macro.

All works fine, but the macro reference assigned to the button in the new file is an EXTERNAL reference to the original file (e.g. 'c:\myprog\myfile123.xls'!macro1). A local copy of Macro1 is actually in the file, but the button contains an external link.

How can I make the button reference an INTERNAL LINK only (just macro1)- so it goes and uses the local copy attached to the file?

Thanks in advance,
Fred