ShellExecute could also be "best way".
Code:
Option Explicit
Private 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 myfile As String
'create dummy file with DOC extension
myfile = "c:\test.doc"
Open myfile For Output As #1
Close #1
'open it in default program
ShellExecute Me.hwnd, vbNullString, myfile, vbNullString, "C:\", vbMaximized
End Sub