[Brian]

The script you'll want to clone/edit is stored inside OmniFocus' application bundle. To get at it, you'll want to right click on OmniFocus, select "Show Package Contents" and then navigate to this location:

OmniFocus.app/Contents/PlugIns/BuiltInClippingHandlers.plugin/Contents/Resources/

You'll probably want to open the "Mail-Leopard" applescript, then save a copy out to your desktop. (Customize a copy, not the original, in other words.)

I think the best way to do this would be to change the way the "on clipping" script handles the MyName parameter.

Just before the "set name to MyName" line, I believe you'll want to insert some script that looks for the appropriate characters at the start of the subject and then trims them out. A google search on "Applescript text manipulation" should return some useful links.

Once you have the customized applescript, store it someplace other than the desktop. At that point, you can duplicate the existing OmniFocus rule, then change the "Run Applescript" line to point at your custom script instead of the one in OmniFocus' app bundle.

Hope this helps!