If you're using XACT it should be easy to do this -
1. Create a reverb effect (under the DSP Effect Path Presets node)
2. Attach the sounds from the cue to the reverb.
3. Create a global variable (say "CaveDistance") and set its properties like range.
4. Create an RPC Preset which will open the RPC editor. Add a curve that's controlled by "CaveDistance" for a reverb parameter (say wet/dry mix).
Now you should be able to control how much reverb gets applied to your sounds by using the CaveDistance variable in the game.
Ashu Tatake
XNA Framework Developer