Changing desktop wallpaper with Conky

[Goombie]

I was wondering if it is possible to create a script (Ruby, Perl, whatever) to do the following things. I would call the script from Conky at a set interval.
I want the script to:
1) Select a desktop wallpaper from one of four different wallpaper lists, depending on the workspace I'm in. The lists would be stored in XML files, in a format like so:
<workspace name="Nature" no="1">
<file>/media/Personal Stuff/Pictures/Wallpapers/Nature/1280x800-wallpaper-2.jpg</file>
More files..
</workspace>
<workspace name="Foo" no="2">
<file>/media/Personal Stuff/Pictures/Wallpapers/Nature/01543_falls_1280x800.jpg</file>
More files..
</workspace>
And so on.
2) Change the wallpaper (in sequential order) at a set interval to another one from that workspace's wallpaper list.
3) Change the wallpaper whenever I switch workspaces to the wallpaper for that workspace.
Essentially, I'm wondering if it is possible to create a script to duplicate the wallpaper changing function of the program Wallpapoz. (http://wallpapoz.akbarhome.com/) I haven't programmed in a long time, so I'm kind of rusty. Any input is appreciated! :D