Hi Richard, Thanks for the exlanation which looks very simple. I often got errors when trying to insert a function within a function. I think I have difficulty to keep track of the number of parentheses. I shall try to keep your example in mind when doing nested functions and if I stumble with a complicated one, I will let you know

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Reply from Richard Rost:

What I tend to do to keep my parentheses straight is to FINISH OFF the parenthesis for the first function and just use a placeholder like XXX for where the second function goes. I'll start like this:

=IF(Grade>=100,"A",XXX)

Now I'll add the part for B in there:

=IF(Grade>=100,"A",IF(Grade>=90,"B",XXX))

And so on.