Confirm box in asp.net

Helloo All,

how to use confirm box in asp gridview when using row deleting event in gridview.... here am using delete (type as image) from command field

i have given below the code which i have using now... but its not working properly...

client side

==========

    <script type="text/javascript">
     function confirmation() {
         if (confirm('are you sure you want to delete ?')) {
             return true;
         } else {
             return false;
         }
     }
    </script>

=========

Server side

======

  protected void gdv_RowDeleting1(object sender, GridViewDeleteEventArgs e)
    {
        
        Session["Agent_Id"] = gdv.Rows[e.RowIndex].Cells[0].Text;
        if (DeleteData())
        {

            lblMsg.Visible = true;
            lblMsg.Text = "Deleted Successfully";
            clear();
            fillGrid();
        }
        else
        {

            lblMsg.Visible = true;
            lblMsg.Text = "Error on Deleting..";
        }
    }

======================================

but its working well when it using button when it call like this

  <asp:Button ID="btnDelete"  runat="server" Text="Delete" OnClientClick="return confirmation();"
                Width="60px" Visible="False" onclick="btnDelete_Click"/>

my problem is how can i call the abouve javascript function in row deleting event....

does any one knows to solve my problem please help me to find a better solution,.....

thanks in advance