How to add keybindings in xfce4

[drife]

Hi,
      Could anybody tell me how to add keybindings in xfce4? For
example, I want to make <Alt>1 as the shortcut for "rxvt".
      I am new to xfce. I used to use Gnome, where I can modify the
settings in configuration editer->apps->metacity->global_keybindings,
but it doesn't work for xfce. I think that is because xfce doesn't use
metacity as the window manager.
      Then, how can I make such global keybinding in xfce?
      Any help will be greatly appreciated.

Thank you.
HM