using a proxy with htmlagilitypack

I searched this question but didn't find anything that I was looking for, basically I want to use a proxy with htmlagilitypack, I had the code to do it before but lost it, here is the code I have so far, which is working. but I timed my self out on a program I was making and need to enable proxies.

    private void button1_Click(object sender, EventArgs e)
    {
        StringBuilder output = new StringBuilder();
        string raw = "http://www.google.com";
        HtmlWeb webGet = new HtmlWeb();
        webGet.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6";
        var document = webGet.Load(raw);


    }