Until the child is ready in THEIR mind to tell you before they have to go OR just go themselves there is NO amount of forcing you can do... :-)
Our daughter was one of those kids that had her 2 yr birthday and took to the potty with no encouragement from us...
Our first son... haha... He was almost 3 when his little brother was born and no amount of trying to get him to use the potty was working. Hubby wanted him "trained" before his brother was born... It always ended up with mommy frustrated, him in tears, and nothing accomplished. So after a week of mommy going nuts and daddy saying "just MAKE him" while he sat at his desk at work... Mommy told daddy that if HE wants him trained... DO IT YOURSELF!!! lol That lasted about 3 hours before hubby agreed that we just needed to back off, and not worry about it. About 8 months later he showed interest and jumped on the potty bandwagon... (he'll be 6 soon)
Now our 2nd boy is almost 3 and I will not stress myself out about it. He will get to it when he is ready... Plus... I am due at the end of the month with our 4th (girl) so I have other things on my mind and in my body. :-)
Boys tend to be closer to 4 when trained... (In MY book a child is not trained until they no longer wear diapers, pull ups, etc AND havn't had any accidents in a month or more) Other wise they are still training... Having a child WANT to train is all about THEIR mentality. SOme are just ready earlier than others...
What is his motivation... It seems like he doesn't care about the rewards, etc... does he care about what class he is in? What his friends are doing? etc?
You may be suprized at howmany boys are in the not trained class. :-)
Good luck!!!