Problem in Warehouse Module

Hi, I am facing a problem while using the Warehouse Mang. Syst Module. When I am making a Movement Wksheet the system allows me to create a movement for quantity greater than the Avail. Qty. But when I try to post the movement it gives an error. I recall that in the demo Cronus co. when ever a Movement such as this was created the system created the Movement where the qty was equal to avail. qty. There has not been any customiztions here. This looks like a setup problem. Can somebody tell me what parameters affect this behaviour. Thanks KMB