Sum in Report derived from an expression

[thudson]

I am trying to SUM the values for Profit in a report from a value derived using an expression. When try to create a Total, using Design Totals, Sum is greyed out.
Is there another way I can total these values. I have tried doing it in a Query but that was unsucessful.

 

[June7]

I've never used Design Totals on report (never even noticed it was there). Just now looked at and Totals is greyed out. Oh, only available in Layout view. I seldom work with Layout view. Arithmetic functions only available if a number value is in the textbox. What is the expression generating value?