The Market Profile books were authored by Jim Dalton, Kevin Koy & Pete Steidlemeyer. Do a google search with those lastnames & the word "profile" together. There are many articles with additional links and profile examples. Check it out.
Hmmmm............the midpoint of the prior 3 days' range can sometimes be the current value point??..............maybe in a sideways market but certainly not in a trending market. I always found it better to look at each day's profile separately in order to get a clearer idea of where support & resistance may occur.
If you have eSignal as your datafeed, you can put a realtime market profile tool on your charts for free. There is a download available from http://www.futurenets.co.uk/.
The add-in plots the histogram on your price chart, with the value area picked out in a different colour from the tails. It can be set to retain the histograms for a variable number of prior days, so that you can see where current action is in relation to the value area of the previous day, etc. The value line is recalculated at intervals during the day.
I have found that to have the price history and the price distribution plotted on the price chart is a much clearer picture of price evolution than the classical MP graphic with alphabetical time periods. Not paying for it is better too.