Calling ASCX user control randomly

Hello, I've a user control I register as follows:

<%@ Register TagPrefix="db" TagName="Banner" Src="~/Banner.ascx" %>

and I call it this way when I need it:

<db:Banner ID="Banner1" runat="server" />


My problem is that the file Im registering (banner.ascx) is not always the same.

Each customer may display a different file, as banner.ascx, or banner2.ascx, etc

The file name is stored on a session variable called banner, so when I try this:

<%@ Register TagPrefix="db" TagName="Banner" Src="~/<%=session("banner")%>" %>

I obviously get an error.

Is there a workaround to assign the name of the user control file randomly?

Thanks.