How to enhance the Tcode(F871) program to create new payment request ?

Hi

My requirement is that create new payment request (F871)

I want to copy the standard tcode(F871) program and make some change like invisible the field and change the level of the field .

  But when I copy the standard program of the tcode(F871) and create a zprogram with a ztcde......execute the tcode(ztcode)....it is showing error before doing any chance in the progam.

So what change I will do in my zprogram so that when I execute the ztcode It will work...........

Regards

Debo