Use enable & disable in Buttons

Hi friends

I am now learning flash Mx
can you help iln clearing my doubts

  1. how to show alert messages
    2)there are three buttons in my project
    button 1, button 2, button3
    if you press button1 button 3 should get disabled and if your press button 2 then button 3 should get enabled
    and also an alert should be displayed at the same time that button 3 is disable or enabled

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