Detecting end of movement


I have an mc that moves into position after a button is pressed. I would like a seperate mc start playing after the moving mc stops. Can someone help me in how this can be achieved? I have attached a sample .fla file that has the parts that are needed.The file was over the allowed limit so I have uploaded it here:

I would like the mc ‘red’ start playing after the mc ‘longBar’ stops moving. The mc ‘longBar’ starts moving after the gray square button is pressed.

Thanks in advance!