Orchterstral strings xfade MW-how to get mw controller

I use Halion as aVST and want to compose with this orchestarl strings xfade MW een fade in with the Modulation wheel ( the name suggests this is possible )
So during recording of this sound i make a adjustment with the modulation wheel of the controller keyboard
How to get this sound controlled by the midi controller during recording ?

The mod wheel is connected to the volume parameter by default in HAlion5 and this automation is recorded in my composer as modulation parameter.
That is not what i want, so i must chance the Mod wheel assigning from the midi controller to expression midi cc, but there is no expression in HAlion
In the composer i can assign a midi controller mod wheel to expression, but in Halion 5 i do need a CC mapper…the mod wheel must be mapped to expression cc
I use the mod wheel from the midi controllerkeyboard during recording in the composer to get a expression controller value for the program(sound) in HAlion 5 and record this expression parameter in the composer
But how to do this practical ?