Keep getting error#1502 for this loop in as3

It's supposed to be for a rhythm game, where while the mc is on the stage, the boolean keeps switching back and forth from true to flase and you have to catch it at the right time. But I keep getting an error...

while (theBeat)
{
  if (theBeat.currentFrame < 5)
    {
    onBeat = true
    trace(onBeat)
    }

  if (theBeat.currentFrame > 5)
    {
    onBeat = false
    trace(onBeat)
    }
}