[Plugin: Visual Form Builder] Add more similar fieldset on form

I want my form to add more similar fieldset by clicking plus button like the one you used in Visual Form Builder > Email Details > E-mail(s) To.

See the screenshot
http://www.freeimagehosting.net/newuploads/885a3.jpg

Fieldset should go something like File 1, File 2, File 3,…so on.

Thanks in advance.

http://wordpress.org/extend/plugins/visual-form-builder/