Recording audio while button is held down

I'm wondering what is the best way for me to record sound while the user is holding down a UIButton. (i.e. start when the user is holding down and stop when he releases the button). Will something like this work?

Function call

button.addTarget(self, action: "holding:", forControlEvents: .TouchDown)

Function:

func holding (sender:UIButton!) {

// Sound recording code here

}

Also I'm trying to update a UIProgressView as the sound is recorded. Is there a way I can access the amount of time (in seconds / milliseconds) that has elapsed since the recording has started? Can I just use my own timer or will there be some dependency?