TI ho corretto il codice... aveviscritto X al posto di Y:

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Public Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
xx = X
yy = Y
End Sub

Public Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = 1 Then
Dvx__Autoplay.Left = X + (Dvx__Autoplay.Left - xx)
Dvx__Autoplay.Top = Y + (Dvx__Autoplay.Top - yy)
End If
End Sub
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OK ???