Intracompany Stock Transfer

Hi

Friends,

When i am doing Intracompany Stock Transfer between two plant under same company code (one plant as customer another as vendor), at the time of STO creation through MEN21N i am facing an exceptioanal problem. Plant at line item level should come automatically during transaction but it is not coming if i enter it manually it's also rejecting.

What will be the solution, can anyone help me.

Thnx & Regards

Amar