how to calculate stock balance in sql server 2005

Hi
I have two relational tables for Goods Receiving like tblReceipt & tblReceiptDetail. In tblReceipt has three columns like ReceiptID,Date,SupplierName and in tblReceiptDetail has four columns like ReceiptID,ItemID,ItemName,Qty
and two relational tables  for issuing goods like tblIssued and tblIssuedDetail. In tblIssued has three columns like IssuedID,Date,Department and in tblIssuedDetail has four columns IssuedID,ItemID,ItemName,Qty.
Now I want to calculate stock balance each item  wise separtely according to the following formula
OpeningStock+Receipt-IssuedStock
in order to known about how much a particular item is received or issued and how much balance is remain in sql management studio 2005
please help me
qayyum
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