Add private mail and tweak escrow payment on a website

this website is like freelancer. but I need to change how the "contact user" private messages are laid out on this website. I would only like the users to interact using private mail when they are engaged in a project. for example a freelancer may contact the employer only after he/she has put a bid. There is already a private message option but there is no control. Anyone can send a message to a user and employer. and there is an escrow payment option. but I would like the escrow to be connected to the project. right now it isn't connected. Thanks, here is my website (i will change the domain later on though) [login to view URL]