You can create a Repeater Region, which is an area of the screen which when the mouse is in that area it broadcasts to the chosen target(s). I'd probably go with a Repeater Region, as this excels for healing.

You could make a mapped key, two steps, set it to advance on press or release. So pressing will turn it on, and releasing will turn it off. Then have Step 1 disable the mapped key which does the mouseover healing and step two enable the mapped key. So while the right button is held, the mapped key cannot fire off.