I have to display some message to the user when he/she tries to modify a project list, e.g. add a new item,
please advise me if this is achievable through the workflow script code
The best you could get is a msgbox in _CanCustomize.
This would be presented whenever a user selects tools > customize, which also covers user maintenance.
Once you're in the customization screen you're outside of the QC project, and the reach of workflow functions.
... just another Tester ...
There is a commercial tool for managing Project Lists available at http://www.qualitycentertools.com/
Tim Mackey tim@QualityCenterTools.com