Stephen,
I have thought about that since posting. You can create a Custom Functoid using .NET classes, by inheriting from the Microsoft.BizTalk.BaseFunctoids class. There’s a sample in the SDK that comes with BizTalk 2003 -but it’s not a database sample.
Ideally it would be great if you could inherit from the standard database functoid, then add another input for a second datase column, but I can’t see any example code that shows how to construct such an input. So I’m a bit stuck.
I hope they have extended this area in the new 2006 version !
-John