Passing Parameters To Extended Stored Procedures

I'm trying to pass parameters to an extended stored procedure, to no
avail. I would like to pass two integers to the dll and I have the
following three snippets:

1. The C++ portion of the dll:
....
declspec(dllexport) int myAddNumbers(int m, int n)
....

2. The creation of the extended stored procedure:
EXEC sp_addextendedproc myAddNumbers , 'foodll.dll';

3. The usage:
create function TestFunction()
returns integer
as
begin
declare @rc integer
exec @rc = myAddNumbers
return (@rc)
end

How do any of the above three things need to be modified in order to
make this work?

Thanks!!!