Take a look at some routing posibilities at:
http://www.internet.com.uy/rere/main/index.htm
In the general purpose recording setup (the 1st one), you can set the monitoring fader to zero (i.e. you will not hear the input signal) while you're still able to record your line in signal unmodified or with effects.
You should install the custom made mixer first though, but this is explained in the pack.
Route the signals going to the mixer inputs IN1 IN2 IN3 from whatever inputs you are currently using (excepting the MAINBUS wires which should be left where they are connected in the photo)
I hope it works for you, please be sure to read the txt files for some info about how to change the port number...etc...
Gonzo