public void initiate(WebBrowser browser)
{
   browser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(refDocumentCompleted);
   // navigate browser to the referal Uri
   browser.Navigate(refreral);

   browser.DocumentCompleted -= refDocumentCompleted;
   //remove here so that it doesn't do this everytime a document is completed, i want it just in this method
}

private void refDocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
    // want to call navigate method on browser here. but Its out of scope.
}

((WebBrowser)sender).Navigate(...);

private WebBrowser _browser;

// inside initiate
_browser = browser;

// Inside event handler
_browser.Navigate(...);

public void initiate(WebBrowser browser)
{

    browser.DocumentCompleted += (sender, e) => {
        browser.DoStuff(); // it's in scope via closure
    };

    // etc
}

public void initiate(WebBrowser browser)
{

    var doStuff = (sender, e) => {
        browser.DoStuff(); // it's in scope via closure
    };

    browser.DocumentCompleted += doStuff;

    // etc

    browser.DocumentCompleted -= doStuff;
}