Does anyone know of a green screen (chroma key) plug for photo-paint? Everything I can find is for PSD, darn it!
Curious, why do you need a croma key for photopaint? Have you looked at stuff like masking, transparent backgrounds, etc. What you say is for video work. I use that a lot in video programs. No need in PP or PS to achieve that end result.
Perhaps explain your goals more.
Maybe not exactly what you seek... but you can create a mask using the color mask tool:
And if you click on the 'More...' button you get a bit more control of the colour masking.
Often a goal is to quickly get rid of backgrounds: I made magic erase to speed up that process for my own production needs. Esp. if you have many products etc to clip out (I was making a product catalog). It's not a free macro but saves several steps per photo.