Stock Transport Orders & availability check

Dear Gurus,

In our company, we are using stock transport orders to transfer material from Central Warehouse ( plant A ) to Regional warehouse ( plant B). Plant B always recieves material from plant A, against customer orders or safety stocks.Sales orders are booked at regional warehouse ( plant B ).

We have used the stock transport orders in avaiability check of the sales orders.Delivery date of stock transport order is caluclated as lead time of the material from plant A to plant B + GRN time. But this information does not give clear picture, since acual stock position in plant A is not reflected in Delivery date of stock transport order.

Can any body inform me how actual stock position at plant A can be used in the availability check of the sales order boked in plant B?