Its possible to use an .ascx from inside a WebPart but not a .aspx unless you load it inside an iframe. An .ascx would typically be used inside a WebPart that is made as a compiled dll but it is more conventional inside a WebPart that is itself a .ascx.

Hope it helps,

Joe 

Hi,

Control c = Page.LoadControl("~/Example.ascx");

if(c != null)
{

   this.Controls.Add(c);

}

or load it into a specific <asp:Panel id="pnlFoo" runat="server"

pnlFoo.Controls.Add(c);

Note that ~/ represents the root of the site, so you need the full path of the UserControl relative to the site root.

Hope it helps,

Joe