Change Stock value in the past

Dear All,

We start our fiscal year in oktober, we are stil working on the closing procedures. When we look at stocks we see that some materials procured externally are valuated at 0 standard price, we want to change the value to MAP but in MR21 we cannot change the price in period 12 2010 because it is not open. Also we would like to valuate the goods movements differently from the time the goods were procured untill now the price should be MAP instead of 0.

How could we do this?

Thanks,

Michaë