You can add a custom field(s) to populate when the material is added to the job. You would set that date on creation with a BPM. It’s probably easier that a change log in the long run.
I created 2 UD Fields on the JobMtl Table. One was called RequestedBy_c and the other was RequestDate_c. I then created 2 BPM Data Directives for the added row to set the UD Fields to: RequestedBy to CallContextClient.CurrentUserID and RequestDate to BPMFunc.Now(). When a new row is added it will look at the Current UserID and the Current date/time. Then you can create a query that will pull this information.