With DECLARE statement you can access only non-COM DLLs (like user32.dll, gdi32.dll and kernel32.dll). So you must not use DECLARE statement for using VB DLL functions. Instead, as I said, you must create instance of the class, declared in this DLL, and call its functions as methods of the instantiated object.
If VB DLL uses another DLL, Declare statement in this VB DLL must have scope, appropriate for the DLL. I'm not sure, but even this Declare statement is Public, it is only for the DLL and these functions will not be accessible out of the DLL.