Custom KPI Questions

Hi -

We're trying to create some KPIs based on account balances and such.  Specifically, we're interested in seeing a "short-term liabilities" number, which includes: AP, Unbilled POs, Credit Card Balance, Line of Credit balance.  AP is an existing KPI, we've got a saved search created for unbilled POs, but are not sure how to go about creating a KPI which simply reports an account balance.

Second, we'd like to actually have netsuite add up all these KPI numbers to give us the bottom line short-term liability.  Is this possible, either directly, via a saved search, or through scripting?

Thanks!