You're right. Thanks, Steve.
I stumbled on the report's SQL for the field I wanted.
My report is based on a query. I got a SELECT into the Record Source that
wanted to lift a field from the table Loan List, but the field was not in the
query.
I did that by dragging the field name "[Loan List].[Percent]" from the Field
List window to the Report Header. When I tried to do that, Access said
"To complete this operation, Access must modify the RecordSource property of
the current form or report. Access will create a new query and embed it
directly into the report's RecordSource property. The report will no longer
be based on the 'ABC' query."
Fine with me, but then the field I chose bore the complaint "Invalid Control
Property: Control Source. No Such Field in the Field List."
This seems odd, since I dragged the field name from the "Add Existing
Fields" list.
Anyhow, I put the field [Loan List].[Percent] in the underlying query, and I
can get the Percent value to show up in the report's header. It's inelegant
in so far as I have to put the Percent in each record of the query, so that I
can get it to show up once in the report's header, but I don't mind!