I have a large invoice database with a calculation field that calculates the total invoice amount less the total payment amount leaving me with the total outstanding.

This field cannot be indexed resulting in the find being very slow.

Are there any tricks that will enable me to speed up this search?

Is there a way to automate the population of an indexed field based on whether an amount is owing in another field or not?

You can use an offline process performed after hours (chron job) to set the contents of an indexed number field to the "total outstanding". This would only be updated once per day and may be incorrect, but finds on this copy of the real field will be fast.

-bd