Ok first of all i recommend using adobe camera raw. set your workspace to adobe rgb and load them in camera raw. forget about DPP there are only limited things you can do in DPP.
if you want to maximize the potential of WB i suggest you do it in camera raw because you can see the values of the RGB so many times all at the same time when you hover over the image using the color sampler tool and mark whatever part u want on the image.
Find a spot in the image that can give you a value of R=125-127, G=125-127, B=125-127.
do not stop until you have seen one. i am sure there is.
when you get that spot that reads like the above click your white balance tool and click inside the circle where your color sampler tool is located. this will give you a correct and accurate white balance.
if you still want to do it in DPP try the double clicking your raw file and open your tool pallete or crtl+T on pc or option+T on a mac and go the the RGB tab.
inside the RGB tab click the eye drop tool and sample on the image or hover on the image. this will adjust the RGB channels according to the spot you sample. try to hover it to something neutral like gray or red or green or blue.. just hover to taste until your satisfied.
on the lower left hand corner of the screen you will see some number like
(560,2789) 234,222,109
the numbers inside the parenthesis represents the the X and Y of the image.
the next figure like xxx,xxx,xxx is your RGB. try to find the sweet spot that can give you values in the middle of 0-255 for all of them.. it doesnt matter if they are not exactly the same but just make sure they are not so much apart. try looking for something like
128,125,127 or if you can find 128,127,127 it would be fine.
there you go buddy.... my novel is finish. i am typing this while lying on my bed with my neck twisted.