Curious about WaitExten

Hello,
In my extensions.conf file I am using the Playback application to play a file called ‘ack’ … So, Playback(ack). Ack plays the following “To confirm that you heard this message, press 1. To replay, press 2”. After Playback(ack), the next line is WaitExten(10) … so it waits for 10 seconds for a response.

My question:
As soon as I hear “To confirm that you heard this message, press 1.”, I press 1 but nothing happens. It always waits to receive the digit until WaitExten(10). Is there some way to “interrupt” so-to-speak the Playback file and press 1 during the message?

Replace Playback() with Background() application.

voip-info.org/wiki/view/Aste … Background