There are times when you need only to sum, or average, or count ONLY if it is based on a certain criteria or query.  It is very to do this in ACCESS but most of us are avid EXCEL users. See below for examples with using grades and percentages.  What is nice about these formulas is that you can use the <, >, <=, >=. <>,  and <>= with letters.

Sum avergae and count If commands