Ermm...isn't the Rascal an audio-only interface? I don't think that it has computer control capabilities.
If this is the case - and I am 99.99% sure it is - then you will need a CT-17 or clone CAT interface.
Take a look at
http://hrd.ham-radio.ch (that's right - NO www) and download the INTERFACING GUIDE
145, Pete PH1PH - G7ECN
http://hrd.ham-radio.ch for HAM RADIO DELUXE. Freeware CAT control, PSK31, logging, sat tracking, remote netork access &c &c &c. Helping you keep your money in YOUR pocket :-)