-- use this to get the system time
set variable = Browser.ExecJS("var d = new Date(); d.getTime();")
-- use this to set a target time
set finish_time = Browser.ExecJS("var d = new Date(); d.getTime();") + ( time_in_milliseconds )
-- use this to get the time difference
set var difference = finish_time - Browser.ExecJS("var d = new Date(); d.getTime();")
-- compare time. you can also check if difference is -/+ value
If (browser_time > finish_time) then tree is finished growing.
This will let you use the local clock rather than calling than making an internet connection