When a user enters a value in one of the fields in a form I want to carry out a calculation and display the results of this calculation before proceeding on to the next field, and all before final submit is pressed.
Part of this process also to take a couple of values previously entered, sum them and show the result before proceeding further with the form.
This will allow the applicant to see if the value he has entered is sensible and will help in interpreting results of data entered later on.
I would prefer to do this in php but not sure how to (as it were) interrupt the input process. I am sure it must be possible as I have seen forms where instant messages are displayed as part of the input process.