how do i set up an external fx unit, logic studio motu 828mk

[felun]

im trying to use an external effects unit on a track within logic, i can understand i will record the effected track back in through the inputs in front of the motu MK11 and into an audio track within logic.

 

but i cant seem to get the single track i want to affect to use a separate output on the motu/logic (all of the tracks are grouped to logic output1-2 except the one im effecting). I was assuming thats what i could use Logic output 3-4 for?

 

how do i make this happen?

cheers