-- Save your current application
tell application "System Events"
	set currentApp to name of 1st process whose frontmost is true
end tell

-- Bring Lync to the front so we can use the menu
tell application "Microsoft Lync"
	activate
end tell

-- Set your status to 'Available'
tell application "System Events"
	tell process "Microsoft Lync"
		tell menu bar 1
			tell menu bar item "Status"
				tell menu "Status"
					click menu item "Available"
				end tell
			end tell
		end tell
	end tell
end tell

-- Return to your previous application
tell application currentApp
	activate
end tell