Ability to solo multiple instruments at once

In the Part List, only one instrument can have the 'solo' box checked. Clicking on the box for another instrument causes the first one to be deselected. I would find it useful to be able to have more than one instrument soloed at a time, so that I can easily listen to a few parts at once without having to click 'mute' on the other parts. This feature is common in other programs, and I hope it's not to difficult to program.

Thanks.