Private Sub SubmitForm(ByVal FormName As String)
    Dim Elems As HtmlElementCollection
    Dim Elem As HtmlElement

    If (WebBrowser1.Document IsNot Nothing) Then
        With WebBrowser1.Document
            Elems = .All.GetElementsByName(FormName)
            If (Not Elems Is Nothing And Elems.Count > 0) Then
                Elem = Elems(0)
                If (Elem.TagName.Equals("FORM")) Then
                    Elem.InvokeMember("Submit")
                End If
            End If
        End With
    End If
End Sub

        private void SubmitForm(String formName)
        {
            HtmlElementCollection elems = null;
            HtmlElement elem = null;

            if (webBrowser1.Document != null)
            {
                HtmlDocument doc = webBrowser1.Document;
                elems = doc.All.GetElementsByName(formName);
                if (elems != null && elems.Count > 0) 
                {
                    elem = elems[0];
                    if (elem.TagName.Equals("FORM"))
                    {
                        elem.InvokeMember("Submit");
                    }
                }
            }
        }