How can i get sum of available qty from inventary.

Hello everyone,

               I did every think for calculating current available stock on particulate product id through abs l language on

import AP.PC.DemandPlanning.Global; 

              but I failed to get value of available stock.

          Can you please elaborate haw can i give sum of available qty on my particulars product through absl language  and this value much be matched to existing customer demand planning screen .

thx.