Hello.  This one is stumping me.  I've created a report that pulls student's scores on tests. 

Test Date   Score1   Score 2
1/1/08        550        550
1/3/08        560       560
1/5/08        590        590
I need the report to give me the difference from first test to last test for both Score1 and Score2. 

A few caveats:  Not every student has taken three tests.  Many take more than three.  I need to subtract the oldest test Score1 from the newest test Score1, the only condition being that the student has taken more than 2 tests.

The score improvement must also be later computed as part of an average.

Many thanks for any help you can provide.

Thank you so much for your reply.  I actually have already ordered your book -- can't wait for it to come.  This global variable concept is definitely new to me.  

I figured out the min() max() analysis yesterday, and went in a slightly different direction.  I created a formula to identify the score as first, last, or neither:
if {tbResult.dateEntered} = Maximum ({tbResult.dateEntered},{tbResult.custID}) then "Last" else
if {tbResult.dateEntered} = Minimum ({tbResult.dateEntered},{tbResult.custID}) then "First" else
"Neither"

I then created another formula to return the first score * (-1) for the min date:
if {@First or Last} = "First" then {tbResult.score1}*-1 else
if {@First or Last} = "Last" then {tbResult.score1} else 0

Those two formulas did what I wanted.  When I tried to  then add the two scores, however, I received an error message stating that Crystal couldn't summarize with the sum() function. 

If I pursue your idea, will this global variable be local enough that it will change on each group (i.e., each student)?  The report will contain information on several hundred students, so the variable is going to have to change each time.

Thanks for your time!

EDIT
I'm definitely on board with your second idea, but I don't know how to assign a Global Variable to the first record.  I declare and assign the variable in the group header.  However, when I try using a formula in the group footer like: FirstScore //the name of the global variable // -  {tbResult.score1}, the formula treats FirstScore as the final record (i.e. the one closest to the group footer when the tests are sorted by date.

Can you give me an example of the exact syntax I'm going to need to use?  Again, thanks for your help.


Edited by PatrickBock - 14 Nov 2008 at 2:57pm