It depends on what veggies they are, what else you eat, and your own personal biochemistry.
In general, eating less than 100g of carbs total (not net carbs, just carbs) will keep you in ketosis. If the amount of carbs in the 3 servings of veggies you want to eat + the carbs from everything else you eat is less than 100g, then you should stay in ketosis.
If you really really 100% have to know, then the best way to check is to get the urine strips that will let you know if you're in ketosis or not.
Scientifically, no one has shown any kind of metabolic advantage for going into ketosis though, and there haven't been enough long term studies to verify that there's no risk from it, so you may want to think about why ketosis is so important to you.
If you really want more info, you might consider picking up Lyle McDonald's book "The Ketogenic Diet" which should have way more information than any of us here could give you on the topic