If you are looking at detail records you will have to add a grouping, then use the revised estimated cost field in the group.  Other option is running totals or subreports

Thanks for the reply.  I do "sum" a grouping in order to get the total "actual" costs and that works fine.  However, I'm pulling those "actual" from the "billing history" file which, unfortunately, does not contain "estimated" costs.

In that group footer where you put the sum you will put just the estimated cost field itself.  That does complicate if you need a total for the report.