Hello Geoff,
I've seen your direct message now. Hm, I'd never trust anything that did something 'automatic' like that, but I accept that some folks might.
I'll get looking re VSTs, but the problem might be that it's one thing to find the Note On item, which will have the Velocity (Volume) setting, but to complete the adjustment you'll also need to change the matching Note Off item, which might come later (usually soon later, but maybe not) and this item will NOT have the Velocity to select by, but it will need changing too. This is quite possible to do, but it makes things more complicated.
I've looked at the DOS Filter utility that I have, and this allows items to be removed from the file based on a velocity range, but does not seem to allow for a Channel to be altered (again, the Note Off will need the same change). The prog I'm looking at will NOT interface with any DAW I'm sure, it's designed to read data from one midi file and output it to one or more other midi files, usually retaining the original file unaltered, just in case it all goes wrong.
I don't at all understand what you're trying to achieve with this, I have to confess. It rather goes against the usual use of midi facilities where the channels control varying volume, pan, everything regarding the instrument selected. I'll have to re-read your original item to try to 'get my head around it'??
Oh, I think I take it that you'r plans relate more to live/real time performance rather than playing midi files - being sure about this may be a help to understanding what your planning.
Geoff B