Chony,
The velocity is data that is stored with the NOTE EVENT, as is the length and the time it is played.

CC (control Change) events affect the note after it has been played, or just prior.But are applied to the whole track at one time and cannot be applied to a single note, unless it is on its own track and channel.

Therefore in this case a CC would not do what you want.

You will need to go into the note edit view and physically change the initial velocity value. I forget now exactly the order that Cubase uses ( I use Sonar) but it odes use a NOTE ON and a NOTE OFF velcity value.

I beleive (as is the case with Sonar) that there will be a midi tool that will enable you to vary the velocities of a whole track, passages or even just specific notes if you use the select by filter tool. Although this WILL depend on what version you have.

Dennis