Is there any way to create random velocities of selected notes?
But controlled by parameters, like "from % to %" or "from value to value"?

VARYVEL.CAL

First off, the Cakewalk Velocity tool affects the entire MIDI track, which makes it useless for drums (unless you want to split everything up).  VARYVEL.cal only affects what you have SELECTED, so that is good.
 
HOWEVER !!!  If you put in a LOWLIMIT of 65 and a HIGHLIMIT of 75, VARYVEL will change that to 20 to 75.  Huh?  Is this only happening to me????  I've looked at the code, and can't see why this is happening. 

Check out the Midi Velocity tool. Select a range of notes, right click the clip(s) and select Process Effect > Midi Effects > Cakewalk FX > Velocity
 
It's immensely powerful and can transform your midi recordings quite easily

Sorry dude, but .... assume you have a drum track with kick, snare, and hi-hat.  Three things.  You can select the kick and use the Cakewalk Velocity tool, BUT !! you can't use the tool on the snare and hi-hat since they'd naturally have different velocity setting requirements.  You can only use it on one thing one time.  Right?
 
The VARYVEL.cal does exactly what you'd need to do this, however it doesn't work.  Other folks have experienced the same random re-setting of the low value as I have.  I've also tried re-writing the code, which didn't work either.  Bummer. 

Yes you're right.
 
But it's easy enough to select ALL of your kick/snare notes etc one at a time and user the tool on just the notes you've selected. Or you can limit your selection to just a few notes or range of notes by click/dragging in the timeline
 
I do this all the time when I can't be bothered to set each note individually

I get the whole selection process. 
 
I want to random the kick between 65 and 75, and random the snare between 95 and 110. Are you saying there is a way to do this?
 
I do now see (thanks) that if I random the snare and the kick by the same amount, then I could use the Scale Velocity process on just (say) the snare to raise it up.
 
Two things are too bad:
1.  that varyvel.cal doesn't work
2.  that there isn't a way to do destructive editing on a MIDI track (i.e., get the kick like I wanted, write that out to a final version where all the changes made by the Cakewalk Velocity tool are hard coded, edit that to fix the snare, ad nauseum)

All non-destructive MIDI edits/processing can be rendered permanent by one method or another (e.g. bounce to clips or process FX)
 
Incidentally, at the time I mentioned VARYVEL.CAL 5+ years ago (!), I was not aware that it had any issues. I get all my velocity variation by recording live MIDI input so I'd never actually used the CAL.
 
 

OK, I <finally> figured it out.  For the Benefit of Mr. Kite, here's how you do it:
 
1.  Open a screenset with PianoRoll or (in my case) an AD2 DrumMap.  Arrange your screen so you can also get to the clip that the MIDI resides in.
2.  Select the kick (or whatever).  Kick gets a hair darker indicating you selected it.
3.  Right-click on the top bar of the MIDI clip.  NOTE:  If you right-click on the clip body, it will undo your selection, and select the whole clip's contents; the clip color should -NOT- change when you right-click it.
4.  Select ProcessEffect, MIDIeffects, Velocity.  Adjust whatever as desired, and hit OK.  Only the kick's velocity gets affected.
5.  Go select the next element, repeat wash, spin and dry.
 
AD2 has some great sounds in it, but the odds of any of those AD2 Beats being the drum part that fits your song is pretty low.   I've had to program the whole damn part, dragging hits around by a 64th note to get it to gel.  The task (as suggested elsewhere) to vary all the velocities one at a time by hand would really suck. 
 
Thanks for your help in my figuring this out.

Glad you go it sussed.
 
It was more or less how I suggested, but it's certainly a fun tool to play around with!