Tenta assim:

 

Public Const SW_SHOW As Long = 5
Declare Function ShellExecute Lib "shell32.dll" Alias _
        "ShellExecuteA" ( ByVal hwnd As Long, ByVal _
        lpOperation As String, ByVal lpFile As String, _
        ByVal lpParameters As String, ByVal lpDirectory _
        As String, ByVal nShowCmd As Long) As Long

Private Sub Command1_Click()
  dim i&
  i& = ShellExecute(0,"open",CaminhoArquivoWord,"","",SW_SHOW)
End Sub