настройка прокси-сервера веб-службы

In c# 4.0, I have a web service called ManufacturerContactDetails. I am calling that web service from a windows app using the following:

var ws = new ManufacturerContactDetailsWebServiceSoapClient();
ContactDetails cd = ws.GetContactDetails("Google");

However, I would like to set the web proxy server that the soap client uses. I've had a look for a ws.Proxy property but it doesn't exist. I don't want to use the one from internet explorer.

How do I set the web proxy server to use?