It depends on so many factors. It's done differently in every state.
at 2:01 PM on Nov. 3, 2008
In my state they garnish somewere around 27% of his paycheck . But it varies alot. Call a lawyer most of them will give you the first visit for free and or they tell you over the phone if you briefly explain your situation
I went to the Indiana government website and assuming you don't work, and they allow you to calculate your weekly income as $0 (they may base it off you making minimum wage) your child support for 2 kids that age would be $147.26 a week. Here's a link to the site:
Your CM page says your in Indiana so that's the page I pulled.