shortage report logic

Hi,

I need logic for material shortage report as

Material  qnty/sale order   stock available   sale order1 sale order2    sale order3

     x                    20                  40             No shortage Noshortage  shortage 20

My X part (Raw material) is calling in different materials. How to calculate the total qnty of X in different materials. How to select the routing which is calling in  Material (production order) if having different routing for same material. This is very aurgent for me. I am not able to define the logic exactly. Please help me.

Regards,

Mastan.