help with part of a game

i know enough to be dangerous on scripting i have a easy game, made the goal and textured the ball, made it physical but what i wanted is when the ball got close to the goal a chain of particles would emit.

I have jopsys particle script, the texture i want to emit .. not sure how to add the sensor to be able to detect if the ball is close to the goal...

Ive been looking at wiki for UUID detect or sensor detect but im lost....


any suggestions?

http://rpgstats.com/wiki/index.php?title=LlSensorRepeat

http://rpgstats.com/wiki/index.php?title=LlSensor

http://rpgstats.com/wiki/index.php?title=Sensor

Or have some phantom/invisible prim and detect collision?