I don't think the actual change that was done in GP will show up in the log will it? The closest I could come to see changes was by viewing the operational log under Event Viewer -> Applications & Services Log -> Microsoft -> Windows -> GroupPolicy. The messages still seem very generic to me.
Starting Audit Policy Configuration Extension Processing.
List of applicable Group Policy objects: (Changes were detected.)
Domain Policy - New
Default Domain Controllers Policy
I hope you get this figured out as it would be very handy indeed. We usually uses GroupPolicyModify but mainly to track systems that failed at applying the newest GPO update..etc