Button

We would like to give our executives a button. When the customer that is browsing the website clicks on this button a small the system will call our executive directly. It would be a computer to phone call. Customer does not need to be logged in to make the call but the other party our executive needs to, so the customer will know they are online and waiting for a call. Dynamically once the call is made the online button should change to busy while on a call. Or if the party receiving the call is not logged in then the button should say offline. When they hit submit the system will call the owner of the button. We have a phone switch for the calls and will like to use asterisk for the platform.