Wiki Billing per E/M coded

[MYAEKEL]

We are a medical billing company that has recently been asked by a physicians office to do their E/M coding. We havent done this before and are wondering how other billing companies charge their clients for this. We were thinking of setting an amount to charge per E/M coded.
If your office provides this service do you have a set amount that you charge your client per E/M coded? If so what is it? Any suggestions appreciated. Thanks.