set procedure to blabla.prg lResult=funcname()Or alternatively you can Set Procedure to OriginalButRenamed.spx or something like that, depending on what you need in each particular situation. One thing to keep in mind is that you don't know if the called program needs some particular procedure file to be open while it runs, so you may need to save the set('procedure') to a variable, then set it to your file plus the old set, then on exit reset it to what it originally was. Placing your file to the beginning of the list should make Fox to find functions in it before finding them in any other file in the list.