so a change on one item in one list, updates one item in another list?

One form library where the updates are submitted and if approved the second list is updated. The form querys the existing data and has a section for adding the updated data. I need the workflow to update only where the criteria is met like [UpdatedProjectName] is not blank.

i would say use an update item action inside a run if action.  place them after your approval actions.

I have been playing around with that and can't get it to work? when I add the update item into the run if box it fails, when I move the update item out of the run if box it works, and can't get multiple run ifs to work, the screen shot is what I have so far and it's working but can't get any kind of nested if functionality? in SharePoint designer you can add as many If's as you need. thanks for any help

Ok what is the failure reason?  in that screenshot your update item is not inside your run if action (the box container).  if you want to nest conditions, you can just place run if actions or set a condition actions inside each other.  the limit is 11 nested conditions.

thanks for responding, above is a sample of the SPD workflow. 20 fields are updated. the field types vary (dates, currency, text, Boolean, number) as well as the conditions. The reason for the form library is for all changes to be approved. The tricky part is almost 100% of the time only a few fields will be updated, so if a user just needs to update Project Status] the workflow ignores the rest based on the conditions. Nintex must have a way of doing this? maybe some custom code? thanks again

The solution was using the Run Parallel Actions, so 20 Run if's check each column before updating, thanks to Cassy for leading me in the right direction but since there are 20 fields it went beyond the 11 deep nesting so I could not use Set Condition.