Form With Realtime Validation

I am in need of something done very urgently. I was asked to create a simple web site that is a form which spans over 3 or 4 pages/layers. However, I require the form to be validated in realtime. This is mainly because I wish to have only the sections required, visible to the user. I was thinking along the lines of using AJAX, but I have no real knowledge of this but I believe this is the best way to create this. The form consists of a large number of questions which uses all of the different input methods (textbox, checkbox, text area, drop down menu, radio buttons, etc) I hope this is actually possible, but please note I am unable to pay more than $100 for this. I understand if this seems to be very low but this was not exactly planned. I require something like the following: Which Scheme Are You With ? New Scheme or Old Scheme What Is Your Name ? {text box} What Is Your Age ? {option of years} --------------------------------------- if scheme = old then show old scheme_info else show new scheme info --------------------------------------- More Questions Are Asked, Then: Which Film Rating Do You Watch ? {checkboxes} ---------------------------------------- if film rating > age then display bad age warning section ---------------------------------------- And the form continues.