PO price grey mode required from all type of PO's

hi,

We have created different PO types. We have the info record for all the materials. If we select PO type and processed the material, the rate is coming under grey field. This is we required. If we process the same material through standard PO, system is allowing to change the price. This we don't want. If we maintained price in info record, either processed through correct PO type or standard PO, system wants to give the price with Grey mode only. This is the requirement. How it be solved? can any one guide me on this.

govind.