What is the switch currently feeding? because this is what you want to be looking at, the switch is just a switch.
EDIT: BTW didn't mean any offence thought you were a member of the public! Turns out you could teach me a thing or two (or three)
EDIT VOL II: just re read and I think I know what you mean. Without thinking about it too much it appears to me that youll need to run more cables. You'll have some kind of 'rose' effort going on in the existing fitting - switch, neutral and loop.You'l have to take a neutral and line (loop) to another arrangement, then take a switch wire from loop down to the (new, additional) switch, then back up to the 'switch' part of the arrangement (i.e. the bit attached to the line side of the appliance). Is that what you were after?