Allow changes to field values to be tested for within a BPM flow

As part of an opportunity approval flow, I need to check if the user has increased the Likely amount.  To do this, I need to be able to set a test within an exclusive gateway to detect if a module field value has changed.  We can do this within the start events so I don't see why we can also do it within the flow.

I would be even better if we could test whether amounts have increased or decreased, or changed from or to specific values.