Help! Scripts and dates

Help! Scripts and dates

Good afternoon all, very new to Zoho Creator, wonder if anybody could assist me.
 
I have a start date box which is populated by me, I would like to populate 3 other boxes from this, however I would like it to add dates:
 
Start Date: 24/08/2011
Reveiw 1: 31 days added to start date
Review 2: 98 days added to start date
Review 3: 168 days added to start date
 
Thanks
 
Martin