Running website with both Basic & Forms authentication

I have some code code in App_Code that I want to expose via standard ASP pages/Forms authentication, as well as Web Services/Basic Authentication.
Currently the folder layout is something like
MySite  
MyPage.aspx  
App_Code     
-> Mycode.cs  
Services     
-> MyWebService.asmx
I understand that if I want Basic authentication for the web service, and forms for the normal pages, I need to convert the "Services" directory to an application in IIS. But once that's done how to I add a reference to the Web Service back to all the code in the root App_Code folder? (without it, I just get missing reference errors when connecting to the asmx page).
...