Don’t. My experience with people that do this is that they usually become clients.
A local DUI lawyer friend of mine in the Cincinnati and Dayton Ohio area, Jeff Meadows, has a solution. He sells a small straw-like device that he claims can predict whether you are over the limit or not.
If accurate, this device might tell you what your BAC is at the time. However, your BAC will in all likelihood continue to go up or down over time.
This can mean that while you seem fine when you leave after drinking, you might not be fine when you get pulled over. It is a good tool to have, but it is even better not to drive after you drink any alcohol.
Read more about the device here: http://www.testorarrest.com/