set up the USB stick on my Macbook
Unfortunately, the most popular tools to prepare USB sticks from CDs/DVDs (WinToFlash and Unetbootin) are not available for Mac OS X, but all is not lost:
First, download and install Virtualbox (free) and and then setup a VBox with Windows (not so free, but obviously you do have a Windows 7 DVD, you might as well use it in VBox, not activated, there is a grace period :). Then get WinToFlash (free again) for your VBox.
Important: enable USB pass-through in the settings for your virtualbox.
Insert your stick into your Mac and unmount it in OSX, go to the VBox menu and mount the USB stick in Windows. Then mount the Windows 7 DVD in the VBox and let WinToFlash work its magic.