If the CX3 doesn't have a 9 or 11 pin cable input, then you can use a Leslie Combo preamp. This is a large footswitch like unit that takes the CX3 outs and routes them to the Leslie, while maintaining full control over the Leslie functions (speed control, fast, slow, brake) as well as gain adjustment.
It's 1/4" outputs into the Leslie Combo Preamp, and then the appropriate 6, 9 or 11 pin to the Leslie (depending on the model you're using).