Pivot Tables, can I use an external list to select data items?
 

I have created a pivot table from a data set. Rows contain Purchase Order
Numbers, data is Open amounts. There are approx 300 Purchase Order numbers
in the Pivot Report. I have an external list of the Purchase Orders I want
to include, approx 175. Is there a way to use the external list to select
the purchase order for the Pivot Report?