In a message dated 14/11/2006 19:06:06 GMT Standard Time, gwinsk@xxxxxxx writes: Isn't the idea similar to that already used by the user defined Decision Height gauges? If so it would allow for the geographical variations in TH, of which Bones spake. Gerry Winskill Yes, I guess you are right. I need to extend my knowlege beyond FS Variables and events though, as this exercise requires we have a variable of our own to store the TL value, an event to save the TL value, and a gauge which detects when TL is reached. Frank T.