The official line is one bar a day, but it is really up to the individual I think. I sometimes have a bar and half a day.
What flavour of bars are we talking about? I ask because the problem with all the bars except peanut and cranberry is that they have more than 20g of carbs each. That is mainly why CD say one bar a day, because that 20g can knock you out of ketosis. But if you are talking about having 2 peanut or cranberry, which actually have less carbs than the shakes, then I reckon you would be fine.
If it is of the higher carb, try cutting it in half, and wrapping the other half up and putting it away (somewhere up high!) and see if that is enough to satisfy your craving.
If not, and you have a whole 20g bar -- no big deal if it has kept you on the wagon. But learn from this, that the higher carb content can give you cravings and make you feel hungry so in future have the rest of your bars much later in the day.