Automated scroll of a webbrowser

I have been able to easily scroll a webbrowser with simple statements like this:

webBrowser1.Focus();
Application.DoEvents();
System.Windows.Forms.SendKeys.Send("{PGDN}");
Application.DoEvents();
webBrowser1.Focus();

This seems to work fine as long as the webbrowser is placed directly on a form. My problem is that in my application, I have placed the webbrowser (actually 2 of them) in a splitcontainer, so that I can have multiple windows that I can size. The problem I have is the above logic does not work for paging down the webbrowser unless I click the webbrowser's downarrow of the scrollbar once. Only then does this logic work.   Any Ideas??