Forms Data Controls :: Pass A Value To Java Script In Aspx Page?

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:ImageButton ID="ImageButton1" runat="server" ImageUrl='<%#Eval("Product_Path","~/Images\{0}") %>'
Height="70px" Width="70px" HeaderText="Product Image" OnClientClick="return OpenPopup() ;" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<script type="text/javascript">
function OpenPopup()
{
window.open(' ','mywindow','width=700, height=800');
return false;
}
</script>

I jast wants to access the ImageUrl value inside the Javascript's function OpenPopup() to open a new window to This URL. All Codes are residing in Same Page.