Restriction in line item deletion of condition record .

Hi friends ,

I have a requirement to restrict the deletion of condition record in va02 like price , commission etc . Restriction also at time of update the pricing condition . I am not able to exactly find out the correct solution in which exit or badi to use . Please help me find out the correct point .

Scenario ...........

In every partial dispatch against whose shipment not completed , smart users try to  change the pricing amount in sale contact to sale in high price for the next dispatch . For that case we have to restrict the deletion of pricing amount and commission and update the same .

Thanks in advance .

Joy.