Yahoo APT service to get Impression counts

Dear YDNers!

We have a Scenario to call a yahoo APT service to get the count of Ad impressions.Being new to yahoo APT development , we need information on
which Yahoo APT service can be used to fetch the impressions count.AFAIK, we need to query Yahoo DB by passing a key (in our case Order number) and
fetch the details of impression count.

Please let me know if anyone has worked on similar scenario.Please guide me to identify the correct services and also how to test the service operation using yahoo
sandbox DB.

This is my first post to this YDN forum , expecting your valuable replies :)other wise you use ReportService in the context of order.