availability check in VL10B

hi,

when I create a STO, and I enter a quantity, the system carries out availability check. and suppose there is no stock.

now when I get stock of the material in the system, and then execute VL10B, still it doesn't create a delivery.

But when I change the PO quantity and save the PO and then again execute VL10B, system creates the delivery document.

So I have concluded that availability check is not carried out by the system in VL10B.

So can anyone tell me how to carry out availability check in VL10B?

please help soon. Will reward points for helpful answer.

Regards

tpk