Price determination in SA

Hi,

I have One business scenarion, Kindly suggest the solution

My client is using scheduling agreement. SA has different rates with different validity say

- Price 1 - valid from 01.04.2012 to 30.04.2012

- Price 2 - valid from 01.05.2012 to 31.05.2012

Now say material is dispatched on 25.04.2012 & received in the plant on 05.05.2012.

Now while Doing GRN system will pick the "Price 2" in price determination as it is valid as per condition maintained.

My client wants System should take "Price 1" as invoice Date is in month of april.

one solution could be GRN can be posted back dated ( April's date) but client is not ready to accept back dated posting.

Kindly suggest the solution

Thanks,

sambhaji