I have a data like below:

IDTest_DateLabEPOTX11110/1/2006110011110/3/20061120111110/4/20061500111110/15/2006281500111110/20/20061400111110/27/2006301500111110/28/20061600111110/29/2006401700111110/30/2006110011111/1/20061200111111/3/20061100111111/6/2006251300111111/7/20061700111111/8/200639.51200111111/9/2006111111/10/2006180011210/2/2006111210/5/20063211210/6/20061700111210/11/2006111210/14/2006200011210/24/200624111210/29/2006220011211/4/200611211/6/2006423000111211/8/2006240011211/11/20062400111211/20/2006230011211/21/20061000111211/22/200635120011211/24/20061500111211/26/200640170011211/27/20061100111211/28/2006130011211/29/20061400111211/30/200611001

What I am trying to do is grab the last lab value of previous month in each ID...