Assign a function key to a push button in module pool program

Hi all,

In my module pool program,there is 4 push buttons on screen 100.Those are SAVE,CLR , REPRINT & BACK.

i want to activate the function keys of computer keyboard

for those push buttons.

i.e F1 for SAVE.

F2 for CLR.

F3 for REPRINT.

F4 for BACK.

plz suggest me how to assign these function keys for those

functions(system commands).it is very urgent.

Regards

pabitra