Issue in check box created in screen 8309 in program SAPMV45A

This should involve not only appending a structure containing customer-  

Specific fields within the tables VBAK, VBAP etc. but also using the     

userexit coding:                                                                               

a)MV45AOZZ for PBO (i.e. module zzmodify_uas_pbo output);                

b)MV45AIZZ for PAI (i.e. module zzmodify_uas_pai input);                 

c)MV45AFZZ (sub-routine USEREXIT_MOVE_FIELD_TO_VBAP) for defaulting the  

  values from the customer master and further processing.