Although it sounds like you may be best using a Gig Script. Something like:
// Convert note velocity to CC value
Var
IAC_Driver_Bus_1 : MidiInDevice // Create an alias for your controller in the Rig Manager
CC_NUMBER : Integer = 55 // Change this to the CC number you want to use
CHANNEL : Integer = 2 // Only convert for notes received on this this channel
//Called when a NoteOn message is received at some MidiIn device
On NoteOnEvent(m : NoteMessage) from IAC_Driver_Bus_1
// Pass through original note on message
InjectMidiEventViaRigManager(IAC_Driver_Bus_1, m)
// Convert note velocity to CC value (only notes on the specified chanel)
If GetChannel(m) == CHANNEL then
InjectMidiEventViaRigManager(IAC_Driver_Bus_1, WithChannel(MakeControlChangeMessage(CC_NUMBER, GetVelocity(m)), CHANNEL))
End
End