I have a custom two custom fields on an opportunity: one is a Lookup field to a custom object and the second for Total Dollar Impact. How can I put the Total Dollar Impact Field amount for the last deal won onto the custom object's tab? Basically, because Opportunity does not have a child-parent relationship to my custom object, I am looking for a way to do a rollup summary for objects with a lookup relationship.
That's not possible without a Lookup or Master-Detail relationship, you're probably gonna need Apex Code or VisualFlow, or both (I can't help you with those)
