Userexit MV45AFZB is used for VA01 wana know where this exit getting input

Hi All,

I have exit MV45AFZB is used in VA01 and i wana know where this exit is getting value from. i just have to change my <b>ship to party</b> from <b>sold to part</b> but befor that i wanted to know what is happen befor this getting value so i can continue my modification.

Tnx in advance