AFAIK it's not possible. But you could create an own logic by using trace to return customized error-messages. This meant using the ErrorMode 0 and querying the ScriptError after each essential load-step. To not cluttering the script too much you could put those logic into a sub-routine similar to this one: Re: TRACE - directly enter an expression which returned the ScriptError and maybe some further results and could also contain an exit script; to break the script on this point.