Midi Volumes Per Track

you could do it by selecting all the notes in the midi track, grab the highest volume note and drag it to your required level, 101, and repeat for your other tracks, that would keep all the notes the same relative to where they were.
 
there may be a cal script you could use similarly by selecting all the notes in the midi tracks and applying it. there is a cal script called 'scale velocity' which will scale all the selected notes by the amount you choose. just tried it out, first time i have ever so much as opened a cal script in all the years i have used sonar/cakewalk products.
 
not really my area but someone will likely come along with the ducks nuts method for you
 
best of luck
 
[edit] there are apparently many cal scripts available to do various things, not sure where to find them, as i said just now was the first time i have ever so much as open cal, there maybe a link in the 'sonar resources and utilities' thread maintained by muidgel, located at the top of the 'software forum' you may find something there

try it in the piano roll view, select everything/all then do it in the velocity pane down the bottom of the piano roll view, there are different ways to do it. can't say i have ever open the event list either 
 
if the controller pane/velocity pane is not visible down the bottom of the piano roll view, go to the top of piano roll view, select view/show hide controller pane

What are you using to generate the sounds? If it's the TTS-1, it has a built-in mixer. Just turn down the volume on the loud tracks, and turn up the volume on the soft ones.
 
If you're feeding a bunch of instruments, you can use the volume controls for the various channels in Console view.
 
If you need to change the actual data, there are ways to do that too and I can walk you through those. But it seems adjusting the mix would be easiest. 

Mmmm...I like the Motif. Good choice :)
 
Circle back when you want to know how to edit the data permanenty, or see pages 184 and 185 in "The Big Book of SONAR Tips."

I'm guessing you're actually more concerned with VELOCITY than VOLUME.
I've had the same problem with drum grooves from various vendors, and here's my fix.  Not the only, maybe not the best, but mine...
1.  Highlight the MIDI clip that you want to amend.
2.  In PRV, make sure your cursor is set to "Move," find the Velocity bars in the bottom PRV Window (there are 3 windows in my PRV - Drum Map, Piano Keys, and Velocity graph).
3.  Raise (or lower if needed) that velocity bar until it's in the same range as the "ideal" clip.  If you've selected the whole MIDI clip, all notes in that clip should change their velocities.
 
Since velocity-sensitive synths will play different sounding notes with higher or lower velocities, this will give you a consistent sound and level out the volume.