Well since Crystal Report questions seem to go unanswered quite frequently on this forum I will take a stab at it. I have never been able to find an official way to over ride the order but I have come up with a hack that may work for you.
For instance, say that you have a report based on an Employee Number where you need to group by the employee number but you want to print out the report sorted in alphabetical order using the employee’s last name.
You can create a formula field using the values of combined fields like this:
Now all you need to do is group by your formula field. This way allows you to combine the Unique or Key field (in my example the EmployeeNumber field) with the first and last name of the employee that may not necessarily be unique into one new field that will definitely be unique. You are still grouping by the employee number but you are using the last name for the sort order.
I hope I understood your question correctly and that this answer makes sense.