Halion Sonic Volume Controls

I have just bought CuBase6 and upgraded the trial version of halion sonic to the full version. Can someone please help with the following problem?
When I insert instruments into the rack and allocate them to midi events, I try to mix the sound by moving the volume level controls for each sound. This works fine until I stop and restart the music in which case the volume reverts back to full, where it started. Is this a setting I have to change? Otherwise what am I doing wrong?

your halionsonic volume can be controlled with cc7 on each midi channel