Control same group of fixtures from two faders

Hi there, I am new to hog 4 and have a hedgehog consul. I am wanting to control a group of led lights from two faders so that I can flash a different color, I though that by having one fader at 90% I could flash a the other color at 100% if they are both set for HTP. But I can not get it to work. Is there a setting I have missed? Thanks Miked