Modify popup message?

Modify popup message?

I have set a workflow to block agents from closing a ticket if there are empty fields (Ticket Type and Category). Doing so skews our reporting.

However, when agents select "Close ticket" they get popups stating “Status has been successfully updated”. But, the status doesn't actually change. I need to modify that so they will receive a "Please complete all fields" message (in RED).

Can this be done?