Charge for voice chat by time with spark

This is my first title in the community.


I need the charge function with spark.For example,the user A is chatting with the user B via spark’s voice chat.There is one button named “Begin Timing” on echo one’s chat window,when the user A click this button,the timer come to work,and the value of the button becames to be “End Timing”.At the same time,the user B also could see the working timer in his chat window.After A clicks the button “End Timing”,the timer stops and B will pay for this voice chat by the time the timer has counted.Only the users who have privilege can use the charge function.The common user cannot use it.

I want to say,is it difficult to implement this function?