Inventory Valuation Difference for Finished Goods

Dear Experts,

I have a following query below when the FG Inventory valuation differences are posted

Finished goods price control is set as u201CSu201D

Eg: In Jan 2010 stock value 1000 ( 100*10)

Feb 2010 , opening stk of 1000 ( 100 units * 10 per piece)

In Feb 2010 , FG price has changed to 12 per piece ( Standard cost estimate executed)

System has posted the price difference entry

Debit FG stock 200/-

Credit Inv Price Diff 200/-

Now the query is, stocks pertaining to Jan 2010 are lying in Feb 2010,

When Inventory valuation is done, my profit is overstated in Feb 2010 for Jan 2010 stocks by 200/-

Is there any way to handle in SAP that it would post the price diff in Jan 2010, instead of Feb2010.

Advance thanks

Sanjai