[AccessD] Exporting Access to Excel - How to "SUM" a column with a variable number of rows?

I am starting to do some experiments involving the creation of Excel
files from Access.

Let's say that I have an Access Recordset that can contain anywhere from
100 to 1,000 records.

I have a little Access application that currently pushes this data into
Excel.  This all works nicely.

What is the best way to "Sum" a column in Excel after the last record,
when the number of records can vary?

Thanks,
Brad