I had hoped to get this from Google forms but, after a quick run through the online docs, it doesn't look nearly sophisticated enough.
Problem: I need an online form where the questions asked are a function of spreadsheet calculations. More specifically, this is for a kid's swimming club, where the user first has to enter a name from a pulldown list. At this point, the form must itself look up a date of birth, and decide for itself which events a child can be entered for, based on the date of birth, the qualification times, and the actual achieved times. Once the app has all this information, it presents a list of checkboxes to the user, asking them which event he/she wants to enter. Finally, it adds up the number of entered events, and tells the user what the entry cost will be, before sending me the name, the list of events, and the cost.
So, basically, it's an online spreadsheet, but with the smarts to send me back each user's entry list and entry cost.