housecor,

RWI's suggestion (PHC02) is an improvement over the IR543 for sending commands: at least it offers all 16 unit codes (numbers). But you will still have to play with the house code wheel to set the house code. Make sure the device you acquire allows you to send ONLY the house code + unit code (ex: M16) and not force you to push a function button as well (ex: M16 ON).

This is OK for a "one time" intervention. Your next step up is a more intelligent device. I believe the cheapest, if you already own a PC, is a powerline interface such as the 1132U or 1132CU. You can then not only send specific commands such as "disable module" but also (depending on what software you get) program conditional triggers...but that's another discussion.