Hi Barry,
There is a series of tutorials at www.axure.com/expert.aspx for basic and advanced features. It sounds like you are getting into some of the more advanced effects pretty quickly.
I've attached a sample of how to create this effect in Axure RP.
The first text field in the sample involves a dynamic panel with two states, one for the normal text field, and one for the highlighted field. The OnFocus of the normal field sets the state to the second state. The OnLostFocus of the highlighted field sets the state back to the first state. The OnKeyUp on the highlighted state uses the action to "Set Variable and Widget Values equal to Values" action to keep both text fields in sync.
The main issue with this is that when the normal field gets focus, we switch to show the highlighted field which does not have focus so you have to click it again.
The second text field in the sample shows how to respond to the mouse moving over it and then off of it. This involved using image map regions and the mouse enter event.
We are working on ways to simplify designing the more common patterns. Hopefully though, learning to use the dynamic panels, events, and actions will provide some flexibility for designing less common patterns.