Two things that stick out... First off, I think you need the Equals(=) sign in front of the function...
Expr1: =GetSumHighest([q1],[q2],[q3],[q4][q5],[q6])
And also, when you set the variables in the function, you don't need the brackets([])
So just use...
arQuest(1) = q1
arQuest(2) =...