We are looking to use RRC to keep track of all our collateral. Part of the information is how much each item costs, and the benefit of using the messy Microsoft Excel is that it is easy to find the total cost of all the collateral. Is there a way to sum attributes of an artifact?

You can do this in RRC today using the built-in document generation capability -- Rational Reporting for Document Generation (RRDG). You would need to create a custom template using the Rational Publishing Engine (sold separately), then load that template into the RRC server. Then when you generate the relevant document(s) by invoking the RRC report wizard, the totals will be calculated.

Alternatively a you could export the data via CSV file and use Excel, OpenOffice, or some other tool to apply formulas on the data.