Wood...
I know squat about the Jandy pda system, but assume it has several relays. If so, you could wire the power supply for the IC60 through one of them. When you select SPA it would energize or degenderize the relay (depending on the type of relay) which would remove the power to the IC60. This of course would only give you an on/off function and not the ability to control the % of output. Turning the system back to pool would turn the IC60 back on.
If this is not enough info, let me know and I'll see what else I can dig up.
Jim R.