Start/stop current timer in Billings

StartStopTimer.scpt

tell application "Billings" to activate
tell application "System Events"
	tell process "Billings"
		tell menu bar 1
			tell menu bar item "Slips"
				tell menu "Slips"
					if menu item "Start Timer" exists then
						click menu item "Start Timer"
					else
						click menu item "Stop Timer"
					end if
				end tell
			end tell
		end tell
		keystroke "h" using {command down}
	end tell
end tell