Hi !
I have a mark table with 4 column as below:

studentID | subject-class | subject-name | mark
001             a01                  a                  5
001             b01                  b                  6
001             a02                  a                  7

one student learned at 2 seminar with the same subject(a).Then, that student had 2 results(5,7). The old result still saved in database. How can i recognize the same subject at report, and choose to calculate the average result in mark column. This case the average point is (7+6)/2.
Thanks!

Edited by anhth - 26 Dec 2010 at 1:39pm

thanks for reply, but it's still not solved my problem. it calculate all of mark. I have a idea ,Can you help me? after I group by subject then i group by mark. Now, mark-group of subject "a" has 2 row(ascending). If i can create a formula field call "unique-mark" from the first row of mark-group. Then, i can take average on "unique-mark".
Thanks!