That format is correct. However, are there any spaces in the filename? They need to be converted to the '+' character. Here is the exact syntax I use for one such AppleScript:
tell application "FileMaker Pro" getURL "FMP7://Username:firstname.lastname@example.org/File+Name.fp7" end tell
Thanks for that. I still can't get this to work. Would having a "•" (bullet) or an "é" (e acute) in the file name be part of the problem ?
I am answering my own question here, but just to let others know that it was the "é" that was the culprit. Apparently accented letters are not permitted. Perhaps this information should be a little more readily available.