[Cjmeck]

I am SO not looking forward to tantrums again... My son was the absolute tantrum king. In the situation you were in, I would do just about anything possible to get him IN the cart. Or stroller or whatever. Get him contained. Water fountains were a good distraction for us for a long time. Give the child a sip of water and it snapped him back to reality. So, find a distraction (no more cookies...lol, I know desperate times, right?) and use that to get him in the cart. Then go about your business and ignore him. If it is something fun (like McD's or going for ice cream or playing at the park) then go sit in the car. If he tantrums again, you go home. I swear I left more public places with a screaming kid in 2 years than most people can even imagine.
At home, I completely agree with what everyone else said. No audience. The larger the crowd, the better the performance so just walk away. Some kids, will calm themselves down. Others (like my son) will tantrum with such intensity that they need help calming down. So after I ignored him for a bit, I did have to hold him on my lap and rock him. He'd just cry until he threw up. Just be consistent, and never, never, never give in once you've said no. Once he's able to communicate better, you'll probably see less tantrums. Oh, and since you took away the nasal spray; could you replace it with a "yes" item instead? Or will he just throw the yes item because he wants the nasal spray? Just a thought, its been awhile. I know I'll be asking you for advice in the not so distant future! lol