I am looking at getting one myself and I think, based on researching what the helix is capable of with out-board pedals, that it is possible. If you get the chance to try this, please let me know if it works.
My thought is, setup your patch with a clean amp model/cab, etc. Hook up the vh4 pedal as such fx send 1 to guitar in on pedal. Return 1 to "to clean amp" on pedal. Then use another cable to hook the "remote" out on the pedal to the ExtAmp in on the helix. Use the fxloop1 block in front of your amp model on the preset to toggle the pedal in and out of the signal chain. Then go to the command center on the helix, select the footswitch that you want to use as the control for the channel switcher. Set it to "ExtAmp" and it "should" work.
Again, I don't own one of the vh4 pedals yet so if you get to try this, please let me know how it goes. I'm very curious.
BHD