VS 2010 - Gridview And Hyperlink Field

I have a gridview with this code:

DataNavigateUrlFields="uId,bUserId,bNavn"
DataNavigateUrlFormatString="Pdfiso.aspx?uId={0}&Over=1&bUserId={1}&uName={2}"
/>

To the hyperlink field I wish to add data from external date, and I have tried this, but it doesn't work,

Code:
Protected Sub Gridview1_PreRender(ByVal sender As Object, ByVal e As EventArgs)
Dim test As String = Request.QueryString("lang")
For Each row As GridViewRow In GridView1.Rows
If row.RowType = DataControlRowType.DataRow Then
Dim grdviewLink As HyperLink = DirectCast(row.Cells(0).Controls(0), HyperLink)
grdviewLink.NavigateUrl += "&lang=" & Convert.ToString(test)
End If
Next
End Sub

I will add the code lang to the URL including the querystring