Make bootable USB from Windows 7 DVD?

I have a Windows 7 Home Premium DVD and would like to install it onto a Retina MacBook Pro. I do not have (nor do I want to buy) the Apple external SuperDrive. I also have access to an iMac with 10.8 installed and would like to know if there is a way to make a bootable flash drive from the DVD so that Boot Camp Assistant will install it. I really don't want to buy Windows 7 again just to get an .ISO file from Microsoft since I already have a license for the DVD copy. I have searched the Internet but all the results I'm finding involve using Windows to make a bootable flash drive from a DVD, and I don't have that capability, as Windows is not installed on the iMac. Thanks.