Analysis Service: filter fact table ?

I have a big table with several types of transsactions: PO (Puchase Orders, SO,( Sales orders), INV (Invoices) ...
I want to create cubes with only one type of transactions (1 cube for PO,...)
Where and how can I filter the rows I want to use in my cube ?
Thankscreate view, and for fact table in AS point at the view.|||create view, and for fact table in AS point at the view.