Flow an attribute based on the change of another attribute.

I would like to flow an attribute based on the difference between another attribute's current  vs. new value.

For example:
If the MV (source) "city" is not equal to the target "city", flow "yes" to "hasMoved".  If the MV/target match, make no change to "hasMoved"

I would like to avoid a rules extension if possible.  Can someone provide a sample?

Mike Crowley | MVP
My Blog -- Planet Technologies