Hi there, this is my forst time to the board. Hope you can help. I am a pilot and I am trying to write a wind calculator program for the Flight Planning Dept of my Company. This is the situation. Environment Canada issues winds (velocity and drection)for certain altitudes i.e. 12000 feet ASl 18000 feet ASL etc. This data is taken from hundreds of stations across Canada. They do not list all the altitudes though. My program will list the velocity and speed at the altitudes not given by Environment Canada. The math is very basic but the progam will save the dispatchers al lot of time. Here is my problem. Wind is given is degrees thus South equals 180, West 270 and North 360 etc. I was using this formula "=MOD(AVERAGE(B5,E5),360)" however wind always increases clockwise as the altitude increases. So if I have a wind at 12000 feet of 340 degrees and 010 degrees at 18000 the program will give an average of 175 which is mathematically correct but not realistic (it would be 355. How can I get the program to always add the average to the first variable...in this case the 340?