Synchronize Robot between Document and Variance

I have a document with a workflow that kicks off upon creation.  I want the workflow for this document to be able to monitor an associated variance for a state change, and when that happens, move the workflow along.

I don't want to have to enter a variance number as a variable.  I just want it to reference the variance that already is linked through the "Changes" tab on the document.

I was going to use a synchronize robot to do this - but not sure of the expression that needs to be written so that it can recognize the associated variance, and watch it for a specific state change (Approved, for example).

Thank you in advance.