Toggle Grids, Guides and Invisibles at once

tell application "QuarkXPress 3.3"
	if exists (document 1) then
		tell document 1
			set baseline grid showing to not baseline grid showing -- toggles baseline grid
			set guides showing to not guides showing -- toggles guides
			set invisibles showing to not invisibles showing -- toggles invisibles
		end tell
	else
		display dialog "A document must be open in order to use this script." buttons {"OK"} default button 1 with icon caution
	end if
end tell