Negative Constaint?

[Ethangar]

Its likely really simple but since this is the first time trying this in XSI rather than LW, I just can't find it.

I am trying to get the nose gear doors to open and close on an helicopter I've done. Its working but I want to go a step further with it.

I have the nulls and parenting set up and the right and left door both open and close fine. I have constraints set on them so they don't open or close to far. So far so good. What I would like to do is have it so that when I open the right door (Rotate the Z 90 degrees) the left door will follow the rotation. Getting it to follow is again easy enough, but... I want it to match the -value of the rotation. So when I rotate the right door null 45 degrees the left door null will rotate to -45 degrees. Right now its just matching it so while one opens the other folds up into the fuselage.

Where would the setting be to make it work opposite to the way it wants?

[Hirazi Blue]

Wouldn't that be easily solved by setting an expression
on the second door (after getting the z-rotation of the
first door into the expression and negating it)?

[Ethangar]

Thanks. Someone else told me to take a look at link with. That got me where I wanted.

Thanks again.