InfoPath Dev

I've googled for ages and keep coming up empty.
I want to open a URL when a user clicks a picture button using the onclick event.
I've found a couple of auggestions using this.external and window.external but neither work.... any ideas?

Background
We have a DDL that is populated with a sharepoint list, when the user is filling out the form they choose a supplier from the drop down. If the supplier has not been added to the SP list yet the user can click the "add new" picture button which will open the supplier list so they can add them.

Next I'll need to find out how to refresh the DDL when the user has added the new list item. So 2 questions in 1!

         This works for the Interneexplorer and for me :)  

            System.Diagnostics.Process proc = new System.Diagnostics.Process();
            proc.StartInfo.FileName = "iexplore";
            proc.StartInfo.Arguments = "http://www.infopathdev.com";
            proc.Start();

Thanks,

When I preview the form and click my button I get this message

System.Security.SecurityException
Request failed.
   at Operator_Vouchers.FormCode.CTRL40_5_Clicked(Object sender, ClickedEventArgs e)
   at Microsoft.Office.InfoPath.Internal.ButtonEventHost.OnButtonClick(DocActionEvent pEvent)
   at Microsoft.Office.Interop.InfoPath.SemiTrust._ButtonEventSink_SinkHelper.OnClick(DocActionEvent pEvent)

Solved it.

advanced form options - security.
Unchecked auto determine. Set to full trust and signed it. Works perfectly now. many thanks.