Identify Simulation cost change from previous rolled up run

Summary:

We are looking for a field or a way to identify what or when is the cost changed of an Item between last roll up and latest roll up date

Content (required):

We are updating a simulation cost book and rolling up daily to keep recent cost updates for report purpose.

We also would like to identify after rolling up, what items are truly changed rolled up cost. Currently Last updated date is by default updating all the items are having rolled up source with the last rolled up date and we are not able to identify truly updated rolled up source items cost change.