Problem: I add a data field to a pivot table, but subsequently can't remove it

Code to add data field:
PivotTables(1).AddDataField PivotTables(1).PivotFields("Revenue"), "Sum of Revenue", xlSum

Code to hide it:
PivotTables(1).PivotFields("Sum of Revenue").orientation = xlHidden

Any ideas? This honestly seems to be a bug to me. Haven't been able to find anything on t'web.

Running Excel 2007 on Windows XP