Trying to Add a listening script for a waterfall

Hi there I was hoping someone could help me out. I am using scripts similarly based on Siggy Romulus' hot tub scripts. I am trying to add a waterfall feature to the hot tub. What I was interested in, is finding a way to have the waterfall texture appear when the water level is at its highest position, and disappear ( switch to alpha texture) when the water level is at its lowest position. So I am guessing the script needs to listen to the touch command on the water level script, but I am not sure how to do this, or what to add to the scripts. Would someone be willing to help?

I have done something similar to this . . . prims linked together using llMessageLinked. The water in the tub was controlled by llSetScale; when the scale reached a certain point, it sent a message to the water to turn on/off.

IM me in SL if you want more information, guidance, or help.

Baron Hauptmann