Back in the days of yore, Photoshop had an option to make all pixels within a certain shade range transparent, which was a real time saver if I wanted to, say, make all the white in an image transparent. Here's what that dialogue box looked like back in Photoshop - though it's been years since I used photoshop, so it may look different now.
Is there anything like this in PxmPro, or is it planned?