Hola:
puedes intentar con esto:
en un timer:
Private Sub Timer1_Timer()
Dim nReturnValue As Long
nReturnValue = FlashWindow(Form1.hWnd, True)
End Sub
y en un modulo:
Public Declare Function FlashWindow Lib "user32" (ByVal hWnd As Long, ByVal bInvert As Boolean) As Long
saludos;