chaker - 2007-09-03

I created a production plan and inventory movements for a product A. the product A=B+C. 

I created the production lines for A. In the production line Tab, the "Movement Quantity" field for A has a positive value and for C and B has negative values (-100). 

In the targed warehouse the product B has 0 in the "On Hand Quantity" field. After posting the production this value changed to -100. I had no message 'product is insufficient on stock'. Why ?