Recalculation of Value field in COPA

Hi,

We have a value field in COPA which derives its value from the UoM conversion maintained in Material Master,

we have now realized that incorrect conversion factors were maintianed in some material master records due to which incorrect values are being displayed in COPA reports.

We have corrected the Material Master records, but how can we update the existing COPA values ?

Regards

Sachin Bhutani