try this little syntax change:
on setfmFileOptions(app_name)
-- choose the Developer Utilities menu item from the Tools menu of FileMaker Pro Advanced
do_menu("FileMaker Pro Advanced", "File", "File Options...")
-- click the "Log in using" checkbox:
tell application "System Events"
tell process app_name
if (exists checkbox "Log in using:" of window 1) is true then
click checkbox "Log in using:" of window 1
end if
end tell
end tell
end setfmFileOptions
You can't use window 1 without telling what process window 1 is in. You'll have to specify app_name as a parameter now.
So, like this:
setfmFileOptions("FileMaker Pro Advanced")