How can I fail based on an exception?

OK.

I have letter grades assigned depending on the mark a person gets, but I need a way to make it so if (for example) H10 (a single assignment, not the overall percent) is less than 50%, then the overall grade is a fail. I can only figure out how to make you pass or fail based on overall grade.

Thank you in advance.

if your grades for each assignment is in A1:H1
=IF(MIN(A1:H1)<.5,"Forced Fail","Normal Average")

If you want a fail when any figure in the range is below 50%

=IF(COUNTIF(range,"<0.5"),"fail","pass")

you could replace "pass" with a formula that calculates the actual grade