FMP + Applescript + Write Access

I have a very simple snippet of code that generates a ‘Write Access Denied’ error. On one table the code works but on others I get the error. All of the tables are in one file that is external to my layout file. I have relationships set up, but nothing that prevents the creation of records

tell application “FileMaker Pro 7”
activate database “APR Library”
tell database “APR Library”
set data of cell “File Path” to myPath
end tell
end tell

In further testing it appears the problem lies with external FMP data sources. I can create tables and layouts in a single file and the script works as it should. When I attach a layout file to external FMP tables the script works for some tables but not all. Not sure if this is a bug or if there is a better way to reference the attached tables. Anyone…?