This might belong in Exchange rather than here but anyways:
I need to send out a sheet with a number of things in need of being graded
(1 to 5).
When I get them back (several hundred) I need to get the average value
(grade) of the returned answers. Some answers will not be entered and hence
shouldn't be used to calculate the average. Another one of the problems here
is that all the files returned might /might not have the same name.