Copying from one list to another, but updating if record exists already?

Our client has a setup with 5 copies of a list, one for each regional branch, inside a single site on Sharepoint 2010. Now, they'd like to have a single list wi开发者_如何学Goth all the records consolidated, once the record is marked as "under evaluation" (simple radio button field).

I went ahead and created a workflow in sharepoint designer, that copies the record from each list to the consolidated one, when the record is edited and matches the status criteria.

Now the problem is that any further edits (as long as the status remains untouched), will create another copy of the record. Say, the user goes and adds an attachment, we end up with multiple copies of a single record.

So, my question: is there any way to update existing records (on another List) in a workflow, based on an ID or some unique value?

i would suggest not using a list at all, but configure a Content Query web part to pull data from the lists at runtime, according to filter.