User exit for lsmw

Hi all,
Im using LSMW direct input method to upload PO. every thing is fine. But when I am checking in ME23n, the PO created does not contain the field GR Based invoice CHECKED ON. Bcause, In lsmw, the structure MBEPOI doesn't contain the field WEBRE.
So, now i want to create an user exit to update the field automatically.
Can any body help me in this.

thanks in advance.
ragards
raj.

there r no user exits for the LSMW

custom screens will not update with lsmw. just check it...

hi..
i have worked ME21N for PO creation ...but i used BDC for the same and for me it is working fine. please check if there is any field exit for WEBRE in CMOD