cross tab sorting issue--sorting icon greyed out

hi, I have a cross tab report report, which “PLSHY—TSY:US” AS cross table, when I am trying to do a sorting on Grand total, which “Grand total” column is a column inserted at right, the “Sorting” icon greyed out. please see the attachment.

Anyone would be able to help? Please
Sorting issue.JPG


lavinaluo (BOB member since 2005-02-14)