Hi,
Hope 1000 and 2000 plants are under different valuation grouping code. If so, get the account modifier assigned to the account assignment category in OME9 as already explained by Dev. Now, go to OBYC and go to GBB. Assign the required GL against the valuation grouping code of 1000 plant and the account modifier and valuation class combination.
If both plants are under same valuation grouping code, then you have to go for different valuation class for the material in both the plants and assign the required GL against the corresponding valuation class.
Regards,
AKPT