Avoid observable dom listener

im trying to build an app with http://reactivex.io/ in JAVA

regarding io.reactivex.Observable;

I have two observables, one of them is a checkbox change event type and the other is a mousemove to capture the cordinates.

I want to combine those two in one observable and then call the subscribe to log the cordinates (done).

My problem is, I would like to wait to the checkbox to be checked in order to add the dom listener of the mousemove observable.

How can i handle this with the observable operators?

Thanks!