Ok, this might work but I havent tried it to be sure.
Go into the advanced programming mode - push the Mode bvutton until your in advanced mode.
Then select the first PROG.MIX1 and push the big button on the far right to open it up.
When your in the next screen RATE should be highlighted. Push the UP Select(cursor) button until you highlight the MIX option - change it from INH to ON.
Scroll down to the MAS option - thats the master chanel. Change it to OFST for Offset.
Scroll down to the SLV option and select the chanel you want to controll.
I dont know if your going to want Link ON or OFF. Id try OFF to start but be prepared to change it. That effects how other chanells work with the same mix so you may need it on.
Next scroll down to SW and select the switch you want to use.
Below that is listed the various positions for that switch. Select the position you want.
next scroll down to Rate and select an offset value. I would hook up a servo and adjust that number as needed.
Exit that MIX and go to PROG.MIX2 and repeat with the apropriate changes. MIX2 would be the same except you would choose a different switch position and a different RATE to get the servo to move to the second position you want.
MIX3, 4 and 5 would start on the second 3 position switch.
I would leave a servo hooked up and watch how the movement changes with each added mix - especially when you add the second switch to things. You may have to go back and forth changing RATE values between the two switches until you get what you want.