Can I see my earnings?

First of all, let me just say that I really like the CRM-system. It rocks! But... I have a question regarding reports. Since sales orders contain both listprice (my buying price) and the sales price, there should be some way of getting reports on how much a sales order generats in profit. As for now, I do this calculation myself and have added a field where I write "earning". But, since I put in the list price, is there no way of creating a report telling me how much I have earned during a month, for instance. Very grateful if somebody could give me a tip? And to the guys at Zoho; well done! Keep up the good work!