outboard effects

[Stoney]

Hi Guys:
Name is Stoney and I am A first time user of this bbs, so go easy on me...
My question is , I am using Cakewalk 6.01
with my pc and a Turtle Beach Systems Tahiti sound card which has only 1 input and 1 output. I want to send my siginal out to my Digitech Studio Vocalist and back to a new track so I can add harmonies, but I have no way to monitor my siginal as I am applying the effect because of the 1 in and 1 out problem. So I can never seem to get the levels right, so I have to tweak and try, tweak and try, and at one point it took me several hours to get at the least; a barely usable set of harmonies!! Can anyone tell me what to do?
Thanks Guys I appreciate the help and If you could e-mail me direct it would help as I don't get a lot of time to check the bbs
e-mail add. is pcmusic@sunlink.net