Wrong. This is not how services works. You don't "run" a Web service by a client. A service is executed permanently on the server side; clients don't activate it. All a Web Service does is receiving HTTP requests from clients and sending back some HTTP response back to the clients, per each HTTP request. And such request can be a request to call some Web method and send the results back to a client.
All you need to know is hot to consume Web Services. It depends on the kind of the service and its spec. To start with some basics, please see:
http://msdn.microsoft.com/en-us/library/aa561062.aspx[
^].
Again, the whole idea to poll some service periodically looks questionable.
—SA