stock transport order, delivery not creating

Dear All

I am trying to creating delivery for stock transport order.

i have define the shipping data for the plants where i have assigned an internal customer.

I have assigned the document type UB for supplying and receiving plant.

I have asigned the delivery type NL to document type and issuing plant as well..

Even than when i try to create the delivery using VL10B, the Stock transport PO is not getting displayed for creating deliver..

Is there any other settings to be maintained ..

Regards

Sarfraz