Grouping based on multiple fields

I am using crystal report version 7.
I am linking the stored procedure to crystal report and display it's fields. I want to create the group having 2 fields and sum the amount field. At present, I can create group with only one field and sum the amount field based on this field.
How can I have the group defined by 2 fields?Create a formula joining the two fields:
{field1}+{field2}

and then group on that formula|||Thanks Anonymous2,
That resolved my problem!