Subtracting subsummary Min from subsummary Max
I am rusty with databases and need some help. I have a file with student test scores and want to know the range (in the sense of the difference between the maximum and minimum scores) when sorting by teacher. I created a subsummary and when I sort by teacher can see the maximum and minimum. Great. But how do I subtract them from each other in the subsummary?
I thought I could do this with GetSummary(Max;Class)-GetSummary(Min;Class). This worked in a smaller simpler file, but not in my real file. I just get a blank field in the summary. The only difference that I can see between the two is that my sort field "class" is coming from a related table. I set up a "class" field in the student table with a calculation to see if this would solve the problem, but still it is blank.
Is there something I am missing? Is there an easier way? I apologize if this is obviously simple, but I am stumped. THANKS!