There are a lot of utilities that will do this for you. Check out Keyboard Maestro, for instance.
http://www.keyboardmaestro.com/main/
But n even better way: rather than limiting yourself to F1 doing just one job, why not have one shortcut that puts the entire Mac at your hands.
For instance, Spotlight can be used to launch apps and open files and folders. Invoke it and type three or four letters from the name and watch the search dynamically adjust.
There are 3rd party apps that are even better than this: LaunchBar
http://www.obdev.at/products/launchbar/index.html
does this and a whole lot more. Invoke the app - I use command-space - and type three letters. It'll find what you're looking for. Better yet, it learns. So first time round type SAF and you'll get Safari. After a few goes SA will do the job, then just S.... Ex fo Excel, Wo for Word and so on.
The advantage over having a keyboard shortcut: you don't have to reprogram it if you change the file you want to open. And it does a whole lot more.
Regards
TD