insert custom item variable through xml in magento admin order detail Magento

Question

Hi I am developing a magento extension in which I need to show a product custom attribute in the magento order detail. I want to add it through xml without editing/ overwriting any core file .. For now i have edit the following file to show custom attribute value app/design/adminhtml/default/default/template/sales/items/column/name.phtml

but I know this is not the correct way. So please suggest me how can I insert it by blocks through xml. Below is the screen-shot link http://awesomescreenshot.com/0e42y3ac8d