Mira, Necesitas un Modulo, Un form y en el Form un Boton
En el Modulo
Public res As Long, returnstring As String * 127
Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Long, ByVal hwndCallback As Long) As Long
Public Sub Cerrar()
res = mciSendString("set CDAudio door closed", returnstring, 127, 0)
End Sub
Public Sub Abrir()
res = mciSendString("set CDAudio door open", returnstring, 127, 0)
End Sub
En el Boton
Private Sub Command1_Click()
If Cdrom = True Then
Cerrar
Cdrom = False
Else
Abrir
Cdrom = True
End If
End Sub
Y en General, Declaraciones del Form
Dim Cdrom As Boolean