Hyperlinkfield report path passed in from code-behind.

I am displaying an asp:gridview of records with a linked list of results;
The first column is a hyperlinkfield of InvoiceNumber; which when the user clicks on it, launches a Reporting Services Report of details for that Invoice Number parameter;
Right now, I have the report path hard-coded and it works nice;
But I cant seem to pass the report server name/path in the code-behind.
Can this be done or do I have to use a linkbutton?

attached is my current code for the hyperlinkfield which works,
AND I am including the non-working code where I try to pass the report name path in the code-behind for the hyperlinkfield.  I add a RowDataBound event to my gridview and code a function in the code-behind.
Protected Sub gvResults_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles gvResults.RowDataBound
            Dim strURL As String
            Dim strPath As String

            strURL = ConfigurationManager.AppSettings("ReportURL").ToString
            strPath = ConfigurationManager.AppSettings("ReportPath").ToString
            strPath = strURL + strPath

            If e.Row.RowType = DataControlRowType.DataRow Then
                Dim hl As HyperLink = TryCast(e.Row.Cells(0).Controls(0), HyperLink)
                hl.NavigateUrl = strPath
                hl.NavigateUrl = "fspInvoice&rs:Command=Render&InvoiceNum={0}" & gvResults.DataKeyNames(e.Row.RowIndex)(0)
            End If
        End Sub

Maybe I don't have the syntax correct but it seems like I have more control over the report and more properties available for the hyperlinkfield.
For example, with the hyperlinkfield, I have target="_blank" so that I can open SSRS report in a new window which helps with our application.
I dont know if that is available for the linkbutton.

thanks in advance.
john

working hyperlinkfield code:
<asp:HyperLinkField 
        HeaderText="ID"
        AccessibleHeaderText="none"
        ItemStyle-HorizontalAlign="Center" 
        ItemStyle-Wrap="False"
        ItemStyle-Width="10%" 
        Target="_blank" 
        DataTextField="InvoiceNum" 
  DataNavigateUrlFormatString="http://allegany/reportserver?/federalsurplus/fspInvoice&rs:Command=Render&InvoiceNum={0}"
        DataNavigateUrlFields="InvoiceNum"
        SortExpression="InvoiceNum" >
<ItemStyle HorizontalAlign="Center" Wrap="False" Width="10%"></ItemStyle>
      </asp:HyperLinkField>

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