MOTM

I'm trying to integrate an pedal into my system.  It has an lfo in it 
and a Passive plug to control the lfo.  Is there a way to take a 
clock signal and change it to a passive signal?  The place where I 
got it from says you can only use an expression or volume pedal for 
this.  By the way it's an infinitphase pedal and it is a sweet phase 
type effect.  
Thanks
JDB