Here a development tool, it prints the onkeyup and onkeydown values of keys to the ruby console.
Of course on PC it's probably useless as the values are standard and published, but for Mac Users it allows you to find out what the values are. In any case you'll also find enclosed the latest list of mac Key values, as known by me and Driven.
To use the tool, start it from the tool menu, then it will print the values to the ruby console, you need to record the key sequence separately to match after.
Given that the most incompatibility between the platform is on the key tests, decide if you want to do separate versions, or make a unique one which will restrict you.
As you'll notice, some keys only have values on the up.
Typically rather than bother with many different keys, I try to group mod keys. Alt (VK_ALT test) would significantly modify the tool behavior; Command (VK_COMMAND test) would change parameters. If there are similar behavior I create a circular toggle on one of the keys, or implement intuitive interface.