Hi,
That feature was not yet done for version 6.0. But it will be available on version 6.1. Checked their roadmap. Now the problem is vtiger didn't release exact release date on vtiger6.1 release.
I have 4 + year experience on vtiger. Hope i can help you on this. Done lots of products and project on vtigerCRM. Just now started working as freelancer. I will do some free customisation if you want, as you are the first client if you provide the job :) I am really looking forward to work with you.
Thanks,
Raj