exclude terms from selecting in taxonomy module

Hi,

I created content type and vocabulary for it. Assigned it for my content type(Required * At least one term in this vocabulary must be selected when submitting a post.). Now i have multiple terms, some of them are parent categories, some of them child categories. Problem is that i dont want people to select Parent categories then creating my chosen content from content type. This is how i want it to work:

Then people create content, they are forced to choose one of the child categories. List looks like this:

Parent category
-child category 1
-child category 2
-child category 3
Parent category
-child category 1
-child category 2
-child category 3
Parent category
-child category 1
-child category 2
-child category 3
So how can i make that parent categories cant be chosen? i googled for this problem but didnt find any solution. :| can anyone please help me?