Turning OFF Effects

Hi folks. I am working on a forest fire scenario. I have set the flames and smoke to appear at a certain time of day, and all works well. As the time progresses more fires start as it consumes the trees. So, once started, the fire burns until it is put out.The thing is, I want to be able to turn the fire effects off by water-bombing them. I figured I would use the proximity tag,then when the water bomber gets close enough the fire goes out....and stays out.I can get the proximity tag to start effects, but I cannot figure out if it is possible to also use it to stop effects once started. Is it also possible to use one effect to stop/replace another effect? i.e. Once "water" has been "dropped" close to the fire, could the fire be replaced by smoke that gradually fades away?Any hints on how to do this would be greatly appreciated.Steve