std price of material at PO level

Hi Experts,

For one of my report, i have done some calucation at PO level based on the STD Price of the PO material.

The report is working fine, but in case the standrad price is changed at the Material master, the report calculations become incorrect. As the material master always reflects only updated Price.

Basically i want to fetch the standra price of that material at the time the PO or GRN was done. When the transaction took place, what was the Standrad price of that material.

Please suggest from where can i get this field data.

Thanks,

Simi