I need help about setting link at URLFOR. Can salesforce do that? I want to use that scontrol when I click 'save' at opportunity and point it to another url. The use of URLFOR I know is with retURL :

window.parent.location.href="{! URLFOR($Action.Opportunity.Edit,Opportunity.Id,
[retURL=URLFOR($Action.Opportunity.View,Opportunity.Id)],true)}";

I can't override button 'save', so I override button 'edit' at opportunity. If only I can use trigger and set url to location I want. Anyone has idea or suggestion? It would be appreciated.