Accessing DLL from Ruby

I have a problem:
I am trying to call a function from a Visual Basic DLL. I wrote following code but Ruby gave error.
I need to resolve this and need expert Ruby?windows help.


#Ruby Program to load dll(Just loading)
require 'Win32API'
dllcalc=Win32API.new("E:\\download\\sudha\\prjCalc.dll","calc",["I"],'I')


# Error 

>ruby dmapi.rb
dmapi.rb:2:in `initialize': GetProcAddress: calc or calcA (RuntimeError)
 from dmapi.rb:2:in `new'
 from dmapi.rb:2
>Exit code: 1



# The Visual Basic Code for the dll. Contains only one function calc. Returns integer, i/p is one integer
# Works OK in VB. The dll was registered in Registry: same error.

Public Function calc(intVal1 As Integer) As Integer
    calc = -intVal1
End Function




# A similar example given in "Pragmatic Programmer"  works finr!

# Please Help

V V Kanetkar