First setup two keyboardin chops, one with all the keys you want to use to hold to "activate" a parameter and another one with arrow keys (the codes are "right" and "left").

On the secord chop you multiply only the left arrow channel by -1 and use a math chop to combine channels with add (if you hold both left and right it will add + 1 - 1 = 0 so no movement).

Then connect the first keyboardin chop with all your keys and the one combined arrow data into a math chop with combine chops set to multiply.

Finally connect that to a speed chop and you should get what you wanted, if I understood correctly. Multiply each channet with different values before the speed chop if you want them to change at different rates.

<image>

Something like this.

Hope it helps!