Hey Rodrigo,
We haven't tried the Ernie Ball MVP in-house but can recommend the Ernie Ball VP Jr. 25k. I believe you need to connect the H9 Expression Jack to the OUT Jack of the Ernie Ball VP Jr.:
http://www.ernieball.com/products/guitar-volume-pedals/2044/vp-jr-25k-for-active-electronics
The MVP appears to use active electronics internally making it a tad more complicated than the Jr. Without a schematic or, most importantly, testing the pedal in-house we're unable to say if it's a suitable expression pedal at this time.
