"I Don't Want to Play..."

...I just want to sit on the potty all day!" Two of the kids I watch during the day are potty training, so we got out the potty seat yesterday. Between the 2 days, Carson has had pants on for a total of about 5 (waking) hours! Tonight at bedtime, I tried to put a diaper on him and the flood gates burst! How do you tell a 2 year-old they can't go potty anymore?