Is there a way to identify how long or when an MRP exception message was created?

[Rryan]

For example, if we have a sales order for a purchase to order material and there is a corresponding open PO.  Let say the sales order is later cancelled.  As there is no longer any demand, we'll get an MRP Exception message of '20'.  Is there a table that shows when the MRP exception message was created?  We want to use that date to find messages created from previous day so we can immediately contact our suppliers to cancel the PO.