Alcohol and INR levels

I am on warfarain and understand I cannot drink alcohol excessively. I am also on phenytoin which contributes to making my INR levels higher, and I just wanted to know how many drinks I could have without making my INR levels too high? Roughly how many points does the INR go up with each drink? And what is the highest number my INR could go up to without becoming a threat to bleeding?
I know there won't be any precise answers as it's different for each person, but I'd just like to know roughly, if that's possible, so I know how many drinks it's safe for me to have. (My range is supposed to be between 2.0 and 3.0).
Thanks very much.