How to make the title bar flash

Create a new .exe project, add a module to it with the following code:

Public Declare Function FlashWindow _
Lib "user32" (ByVal hwnd As Long, _
ByVal bInvert As Long) As Long

Put a timer and 2 commandbuttons on form1 with these properties:
command1.caption="Start"
command2.caption="Stop"
timer1.interval=500 'flashes every 1/2 second
timer1.enabled=false

Code

Private Sub Timer1_Timer()
a& = FlashWindow(Me.hwnd, 1)
End Sub

Private Sub Command1_Click()
Timer1.Enabled = True
End Sub

Private Sub Command2_Click()
Timer1.Enabled = False
End Sub

Execute the app. (F5) and click the buttons.