Develop Wordpress/Buddypress extension/plugin

Hello! We are developing wom intranet social network, based on Wordpress+Budypress and there is a need for a custom feature. We need an ability to ad tiime count on some posts, for a reason. And the reason is – when the post is some new instruction for coworkers, i need them to read it and accept. And i whant to know, how long did theu readed it. Like if Janis read it fot 1min, then i know that he could not read all instruction, but Anna read it fot 7min then probably she done it right. So... Budypress user opens post, time count starting, he read the post and accepting it (or just closing) and i see in some log, how long did this user read the post.