How to set TargetContrlID in ModalPopupExtender with a control in a GridView

How can I set TragetContriID to a HyperLink that is inside a GridView?

I tried this :

<asp:ModalPopupExtender ID="ModalPopupExtender1" runat="server"
                        PopupControlID="Panel1" 
                        CancelControlID="btnCancel" 
                        OnCancelScript="HideModalPopup()"
                        TargetControlID="GridView1$HyperLink1">
</asp:ModalPopupExtender>

But I have an error: that there is no GridView1$HyperLink1