What about what I want?

If I hear the words "I want" one more time tonight I am going to completely lose it. I took the boys to Target this afternoon to get a few things we needed and EVERY single sentence out of Collin's mouth began with the words "I want". At first I didn't really pay any attention but suddenly I realized I was saying No a lot so I just stopped responding and started listening to what he was saying. Mommy, I want that. I want M&M's. I want a DVD. I want a book. I want to eat soap. ( I did tell him we don't eat soap) I want Thomas (we were in the toy aisle looking for a birthday present, otherwise I avoid those aisles). He kept up a steady conversation, all of it about what he wants. How do you eliminate that phrase from a 2 year old's vocabulary? I've explained till I'm blue in the face that you can't have everything you want but you can't rationalize with a 2 year old.