Private Declare Function ShellExecute Lib "shell32.dll" _
    Alias "ShellExecuteA" (ByVal hWnd As Long, _
    ByVal lOperation As String, _
    ByVal lpFile As String, _
    ByVal lpParameters As String, _
    ByVal lpDirectory As String, _
    ByVal nShowCmd As Long) As Long

Private Sub File1_DblClick()
  With File1
    If .ListIndex > -1 Then
      ShellExecute .Path & "\" & .List(.ListIndex), "open", "", "", 1
    End If
  End With
End Sub