I want to be able to ignore a blank score when I am trying to apply weights
to different assignments on a gradebook. An Example would be to apply a
weighted average to three grades, i.e 7points of a possible 10 for the first
grade, 40 points of a possible 50 on the second grade and 0 points of a
possible 30 on the third grade. This is necessary if one of several students
is absent and not required to make up the third assignment. All of the other
students would have scores grater than zero on all three assignments.