Vista - Multiple partial classes for an aspx page

Dear All,

I have been working on a transformation project in VB.Net 2.0. I have
to reuse existing code, in the existing code UI and BL are being
written at one place. I have been working in WebSite type of project,
I need something similar to this:

- I have a page Default.aspx (that will contain all UI controls)
- Default.aspx.vb with the class name _Default (it will contain events
handled for the controls)
- DefaultBL.aspx.vb (this should be a partial class _Default the same
class defined in Default.aspx.vb)

If I define my BL class as a separate one, then I would have to
introduce some model that I am not willing to due to constraints of
the project. I can accomplish the above scenario using WebApplication
but finding no way to achieve it using WebSite. Can someone please
help me out in this regard?

Regards,
Warfi