user exit for ME31k

Hi ABAP Gurus,

I have a requirement for progarm sapmm06E, screen number 220 (Me31k transaction) where the "net price" field automatically populates from the Inforecord price. The requirement is to make the "net price" field blank.

Is there a user exit that can be used for this? The system is R/3 release 4.6C.

Thanks!

Paddy