I would say that the FIRST thing to do if your dog ingests chocolate is DO NOT PANIC...

Much of what I've seen written about canines and chocolate would have you believe that it is the next-most-toxic substance to rat poison - and that you need to break speed-limits and disregard RED traffic signals to rush the animal to a vet (and spend multiple-hundreds of dollars) to have its stomach pumped.

As one who's dogs gobbled-down 2-1/2 pounds of premium chocolate candy in one `sitting', take a deep breath... induce vomiting with several courses of hydrogen peroxide squirted gently into their slightly up-turned muzzles (to avoid aspiration); one teaspoon per 10 pounds of body weight is recommended (
http://www.petplace.com/dogs/how-to-induce-vomiting-emesis-in-dogs/page1.aspx) - easiest if you have- or pick up an oral syringe. 3- to 4 doses administered every 10 minutes - with moderate walking (up- and especially DOWNstairs worked best for me) to make sure the peroxide works its foamy magic.

The after teh second dose the doggie gets that distinctive `...I don't feel so good...' look, and the deed is usually accomplished the next dose.

Try to ascertain how much the dog consumed, and compare that quantity to what comes up...a repeat course might be necessary to cleanse the stomach.