Deletes a field set that was created using the AddFieldSet method. The field set is removed from the PivotTable view and from the PivotFieldSets collection.
expression.DeleteFieldSet(FieldSet)
expression Required. An expression that returns a PivotView object.
FieldSet Required Variant. The name of, or a reference to, a custom field set.
The following line of code deletes a custom field set named "Variance" from PivotTable1.
PivotTable1.ActiveView.DeleteFieldSet "Variance"