Passing Values To Another Page From A Gridview Using Querystrings

I'm trying to use hyperlink fields in my gridview to pass certain values into another page using querystrings. On the next page I've put 'labels' that should be populated with data from the gridview, however nothing happens. This is my gridview code:

"<asp:GridView ID="GridViewGuitars" runat="server" AutoGenerateColumns="False"
DataSourceID="SqlDataSourceGuitars" DataKeyNames="ProductID" BorderColor="White">
<Columns>
<asp:BoundField DataField="ProductID" HeaderText="ProductID"
SortExpression="ProductID" InsertVisible="False" ReadOnly="True"
Visible="False" />

[code]....

And this is the code behind file on the landing page:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

Dim ProdID As String = Request.QueryString("ProductID")
Dim ProdName As String = Request.QueryString("Prod_Name")
Dim ProdPrice As String = Request.QueryString("Prod_Price")
Dim ProdStock As String = Request.QueryString("Prod_Instock")
Dim ProdDescrip As String = Request.QueryString("Prod_Descrip")

[code]....