4. %VALUE% is not related to validation errors!
"Any good resource you can suggest to learn Script Logic in depth?" - not a lot!
1. Help for script logic (not always up to date)
2. SAP notes (search for script logic)
3. Forum search
4. ABAP debug of script execution.
For example the document http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/e025fa8d-1c22-2e10-cd9f-c488c7eeadd4?quicklink=index&…
provide only basic info with some mistakes...
Vadim