Message no. 06207 error while foreclosing PO

Hi all,

Scenario is : Po created for 100 Qty 10 per pc. GR done for 80 qty. Now user wants to foreclose this po but message no 06207 effective price - material price error comes as MAP pf material is changed.

This is project stock. WBS assigned in PO. SO if i simply tick Del Completed indicator and save it allows but does this unlock the budget (hold for 100qty in po)? Or have to change qty to release budget? But chnging qty gives error as effective price different from material price coz of tolerances..

Is there any other way to foreclose po which also release budget.??

Plz suggest..