Change "space" or user

Is it possible to use applescript to:
a) change to a different “space” desktop for the same user?
b) change to a different user (who is already logged in)?

Hi Gary

welcome to Macscripter

yes, but the spaces menu must be enabled in the menu bar and GUI scripting must be enabled in System Preferences

property favouriteSpace : 3

tell application "System Events"
	tell process "SystemUIServer"
		tell (1st menu bar item of menu bar 1 whose value of attribute "AXDescription" is "spaces menu extra")
			perform action "AXPress"
			delay 0.2
			perform action "AXPress" of menu item favouriteSpace of menu 1
		end tell
	end tell
end tell

yes, take a look at 10.3: Use fast user switching from the Terminal. The script is written for Panther,
but the last comment shows to adapt it for Tiger (works also in Leopard, I use it myself)