Doesn't sound like reprogramming will help. If alarm/horn sounds when you press the buttons, then signal is being received by alarm brain in car.
Could be as simple as wiring to central locking system is disconnected. If you can double lock your car with your key from the trunk, then I think the central locking system is still working...hope these hints help.
<span style='color:green'>1994 325i </span>- - - 75,000 mi.
No mods - - - very happy as is!
<span style='color:green'>1995 525i </span>- - - 154,000 mi.
No squeaks or rattles... unreal!