Can I bind two arrow keys to a single shortcut? I'd like to be able to bind a shortcut key to perform differently when pressing two arrow keys than when pressing one or the other. For instance, I want to make a new shortcut key for Command+Left+Up that will be different from Command+Left and Command+Up. 

Is this possible?

I'm using OS X 10.9 - Mavericks.
You could use a private.xml like this with KeyRemap4MacBook:

&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
    &lt;name&gt;test&lt;/name&gt;
    &lt;identifier&gt;test&lt;/identifier&gt;
    &lt;autogen&gt;__SimultaneousKeyPresses__
    KeyCode::CURSOR_UP,
    MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_COMMAND | ModifierFlag::NONE,
    KeyCode::CURSOR_LEFT,
    MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_COMMAND | ModifierFlag::NONE,
    KeyCode::F19&lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;


Then use F19 as the shortcut.