[confused teacher]

Hi, I am trying to develop a formula that will only fill the final grade of a
student in the event that there are two grades allocated in the results
column. I have the formula to assign the letter grade worked out, but because
the value of the source cell is '0', Excel automatically assigns a 'F' in the
cell (B13) (and rightly so as the formula is simply doing what it is told).

I have 2 seperate scores, one each stored in cells D13 and E13, these are
summed to give a total score out of 100 and this result is stored in cell
C13. Based on the following formula :
=IF(C1384.99,"HD",IF(C1374.99,"D",IF(C1364.99," C",IF(C1349.99,"P",IF(C1342.99,"PC",IF(O7=0,"F" ))))))

I need the result in the format of a letter grade in cell B13 based on the
formula above, however I only want a value displayed in cell B13 if the
criteria below is met:

A grade is assigned in each of cells D13 and E13.

If anyone has an answer it would be greatly appreciated.

Brian