Edit and change another field

Edit and change another field

Hello

I have a form with a money value that when OnAdd, add this field value to a "total" field on another form - something like "PoorMan groupsby"...

My problem is when I edit the records I don't know how to update the "remote" record. What value should I add? The diference between the initial and the edited? It seems good idea. But I can I keep a variable from the onEdit-onLoad to the onEdit-onSuccess?

Thanks

Hugo