Clever contact form script

Hi Warriors

I recently saw a video demonstrating a very clever contact form. -or at least I thought it was clever.

What happened was the visitor would input for example their name and email as is normal for a contact form. The clever part was once the first few characters of the second field were entered an additional field appeared requesting another piece of information ie their phone number. Each time data was input in the new field an additional field appeared.

The beauty is people are not likely to populate a form with multiple fields but once they've input data into a couple they are more likely to complete teh form once they've begun. The rule of commitment and consistancy obliging the visitor to complete what they started.

The presenter demonstrating the form said that in testing the form converted very well compared to a form where all the required fields were already populated.

For the life of me I can't find the video I watched or rememebr the name of the script or form. Can you help? Do you know of an open source script that extends a contact form as the visitor adds data?

Thanks in advance for your replies.

Nic