One ounce of vodka has about 65 calories. Vodka contains no fats, carbohydrates, protein, fibers, sugar or cholesterol, so what exactly does vodka contain? A small amount of water, and: ethyl alcohol. Since water has no calories, the approximately 65 calories per ounce of vodka come from: the alcohol itself.
So what happens when you "cook off" vodka? You place the vodka over high heat and shortly, the alcohol begins to evaporate. What does this mean in terms of the calorie content of the vodka still in your saucepan? It means there are fewer calories.
HOWEVER, here is the catch: there is also less vodka in your saucepan. In fact, if you boiled off all the alcohol in vodka (and the water in vodka), you'd be left with an empty saucepan. Not only this, but ALL the flavor of vodka is in the alcohol itself. Less alcohol = fewer calories, but, less calories = less vodka itself = less taste. If you heat vodka until the alcohol begins to evaporate, you are not left with a "more potent" or "more flavorful" essence of vodka in the pan.
Vodka is not like other wines and spirits used for cooking: if you cook red wine (which contains sugar and starch), you end up with a delicious and thick "red wine reduction" that may, at some point, contain no alcohol at all. When cooking with sherry, rum, or scotch, it is also possible to "cook off" the alcohol (and alcohol's calories) and still be left with something flavorful in the pan. Not so with vodka: in vodka, the alcohol IS the flavor.
What does this mean for you and your tasty vodka sauce? It means that if you normally use 1 cup of vodka per batch of sauce, there is no way to add 1 cup of "cooked off" vodka that will be any different in calorie content than vodka straight out of the bottle. You could pour 1 cup of vodka into a saucepan and "cook it off" for 30 minutes, but if you measured the vodka in the saucepan after you were done cooking it, it would be less than 1 cup, and therefore less than your recipe calls for. And, you would have just wasted the vodka you cooked off by pumping it into the air-- breathe deep! (If the vodka in the saucepan is still 1 cup, that would mean you didn't have it on high enough heat to cook any alcohol off, which would mean you also did not cook off any calories.)
However, since you are interested in overall calories and nutritional information, it may be worth noting that research suggests consumption of alcohol actually increases metabolic rate significantly, meaning the body actually burns more calories when alcohol is ingested. So while adding vodka to your sauce may increase the calorie count, it might also step-up the metabolism of the person eating your sauce, causing them to burn more calories than they normally would have.