EXS 24 Logic Sampler Users Group

In your environment, the Physical Input object will probably be 
directly connectedto the "to Recording & Thru" object.  Select the 
connecting cable (and not any object?) and delete it.
Now create a new transformer and cable it between these 2 objects, so 
that you have PhysIn -> Transf -> ToRec.
Double-click the transformer to open its window and set it to
- Apply operation and let non-matching events pass thru (the default)
- In "Conditions" set
   Status: '= Control'
   Cha: All
   -1- : 1
   -2- : All
- In "Operations" set
   Status = 'Thru'
   Cha: Thru
   -1- : 'Fix 7'
   -2- : Thru

Now all incoming controller-1 data (mod.wheel) will be transformed to 
controller-7 (volume).
If you need this sort of stuff more often, you could insert a Cable 
Switcher before the transformer, so that you can bypass/insert the 
transformer in the midi-chain with just one simple mouseclick.
Hope this helps.