using AJAX to show master-details results on same page

I have a registration page that gives a user a drop-down list of staff names, where the user chooses his/her name,

and then chooses and event and a date and then clicks "Submit." This action takes the user to an action page where several

responses are possible. We check to see if the user has already registered, and we check to see if the event is already full.

We also check to validate if the user selected the necessary fields. Appropriate messages appear, depending on the

database results. If the user needs to take an additional step, he/she is directed to hit the "Back" button and

choose another date, for example.

It seems that AJAX could do all this and show it on the single registration page. And when the user has completed

the registration successfully, then an appropriate message would appear right below the Submit button he/she

just clicked.

The action page connects to several different databases in order to process the registration. One connects to the staff list and verifies

the employee ID. A second checks the count of the event and whether this empID is already there.

Can ColdFusion, and perhaps JQuery, perform all this so that the user doesn't have to go to another page and then click

"Back"?

Json has something to do with this database call, and from the Google hits I've tried, I can't get data to flow back into the

AJAX container DIV. There's no error message(a Good Thing), but there's no data, either.