Urgent! - Price Determination User Exit - USEREXIT_XKOMV_FUELLEN

Hi,

We have a requirement wherein I have to maintain some custom logic in the user exit USEREXIT_XKOMV_FUELLEN (module pool SAPLV61A, program RV61AFZB).

Can you please let me know on how to proceed to make changes in this user exit.

Is it through CMOD... If it is through CMOD what is the enhancement that I have to enter.... or If I have to register just like we do when we create a new requirement (pricing)...

When I tried to modify directly, the system is asking for an access key...

Thanks in Advance.

Sincerely,

Vidya