if bool = true then ...

Public musiconoff As Boolean
Declare Function sndPlaySound Lib "winmm.dll" Alias "sndPlaySoundA" (ByVal lpszSoundName As String, ByVal uFlags As Long) As Long

Private Sub Form_Load()
musiconoff = False
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
musiconoff = False
End Sub

Private Sub Label1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If musiconoff = False Then
Dim a As Long
a = sndPlaySound("C:\Sonidos\clic.wav", 1)
musiconoff = True
Else
musiconoff = False
End If
End Sub