Question about using Next/Prev buttons and Contact Form 7

I am working on a multipage client profile using WP UI and wpcf7 and I am looking to check for errors when a user goes to the next tab. I assume this can be done through modifying the next/previous buttons in some way but I can only find the code to change tabPrevText or tabNextText.

I understand this is above and beyond the normal uses of your powerful plugin, but would be very appreciative if you could point me in the right direction.

Thanks

http://wordpress.org/extend/plugins/wp-ui/