Display Count of Prior Orders Submitted by Customer Number

Display Count of Prior Orders Submitted by Customer Number

Hi -
I have a product ordering form that includes a Customer Number field.  I would like to display a count of prior orders by that Customer Number as a new order is being placed.  No detail of orders needed; just a count of the instances that Customer Number appears in all order forms.
I know a pivot table can do a count like this, but am looking for more of a dynamic lookup based on the user entering the Customer Number.
Thanks.