expression question
 

I'm sure this must be easy to do but I'm unable to find any decent help in the docs.

I have a joint rotation that I am using to drive the rotation of a different joint. I used the conecction editor to to connect the output rotation in z of joint 1 to the input rotation in z on joint 2. Now this worked fine and dandy. But ... it doesn't work in the other 2 axis, or more precisly it does but I want to reverse the effect. So how do you write and expression the connects 2 attributes but reverse the 2nd one? I tried the following below but it didn't work. I have the idea there would have to be brakets in there somewhere but I'm not sure where.

giant_eagle:wing_shoulder_r.rx = giant_eagle:wing_shoulder_l.rx -1

Any help for what I'm sure must be a simple answer would be much appreciated.

Cheers.

I've sorted it ...

giant_eagle:wing_shoulder_r.rx = (giant_eagle:wing_shoulder_l.rx * -1)

Cheers.