Editing the text of a textblock in a xaml file ?

 My silverlight code in ASP.NET

  <asp:Silverlight ID="Silverlight1" runat="server" BackColor="#EBEBEB"
BorderColor="Black" BorderStyle="Dotted" BorderWidth="5px" Height="312px"
Source="~/Page.xaml" Width="442px">

  And in that source Page.xaml file I have.
 
<TextBlock Width="97" Height="28" Canvas.Left="261" Canvas.Top="204"
Text="TextBlock" TextWrapping="Wrap" x:Name="textblock1"/>
 
 How would I edit the contents of that textblock1 in VB? textblock1.text = "hello" is the obvious solution to me ...