2000 Ford Ranger

There is no unprogramming. But you can try this with the Ranger transmitters:
PROGRAMMING REMOTE TRANSMITTER Ensure anti-theft system is not armed or triggered. Cycle ignition switch 8 times and end in RUN position to enter program mode. RAP module should lock and unlock doors to confirm program mode has been entered. Within 20 seconds, press any button on transmitter(s). Doors will lock, then unlock to confirm that each transmitter has been programmed. Repeat for each transmitter. If door locks do not respond for any remote transmitter, wait several seconds and press transmitter button again. If door locks still do not respond, go to SYSTEM TESTS. Turn ignition off or wait 20 seconds after last transmitter to be programmed to exit program mode. RAP module will lock and unlock doors to confirm programming. NOTE: All keyless entry remote transmitters must be programmed at the same time.

Try getting one from the junkyard, these are fairly expensive little buggers. I cant gaurantee it will work as you plan, it might if it's done with the Ford scan tool. By this method?