call an executable of OOaml from VBA
===

I have coded a very simple `hello.ml` in OCaml:

    let () =
      print_string "hello world!\n"

then I compiled it by `ocamlc -o hello.exe hello.ml`, and `./hello.exe` under a terminal does return the string.

Now I would like to call it from a VBA code. I open a Microsoft Excel file, and the VBA editor, and put:

    Sub run()
        Dim Result As Variant
        Result = Shell("C:\test\hello.exe")
    End Sub

I would expect `Result` get the string `hello world!`, but running the macro gives me an error `Run-time error '5': Invalid procedure call or argument`. 

Could anyone tell me what is wrong?