Dale,
Thanks for the tip. Here's how I wound up solving this:
'Select the sheet I want to work with
Worksheets("Quarterly Totals"

.Select
'Select first cell below headers
Range("A2"

.Select
'Note: only needed last row since last column is static
' in this situation
Selection.End(xlDown).Select
strLastCell = "'Quarterly Totals'!R1C1:R" & Trim(Str(Selection.Row)) & "C13"
'Update the range for the Pivot Cache
Worksheets("Total T&E Exp Pivot"

.PivotTables(1).PivotCache.SourceData = strLastCell
'Get rid of any old values in the Pivot Cache
Worksheets("Total T&E Exp Pivot"

.PivotTables(1).PivotCache.MissingItemsLimit = 0
'Refresh the Pivot Table with the new data from
' the PivotCache
Worksheets("Total T&E Exp Pivot"

.PivotTables(1).PivotCache.Refresh
I like your approach of going bottom up to find the last row, although in my application, I know that there will be no blanks in my first column, so starting from the first cell and going down works.
Thanks again for your help.
The Wip