Your if statement is all mangled now. You are saying if value isn't highest or lowest then calculate the average. So if your last value input is the highest or lowest you won't even average.
At this point you aren't taking the values out that you don't want. So your average after the loop equals the sum of ALL values. You have the correct value of lowest and highest but you need to remove the sum of the two from your average before executing.
Make sure to remove that if statement because it doesn't do what you think it does.
You are very close though.
