The Accumulation / Distribution line was created by Marc Chaikin to determine the flow of money into or out of a security.
For each day, first calculate:
[(Close - Low) - (High - Close)] / (High - Low) which will give a number between +1 and -1.
And then multiply the result by the Volume, and add to the cumulative total.
In other words the closer the Close is to the High, the more Volume is added to the cumulative total and the nearer the Close is to the Low, the more Volume is subtracted from the cumulative total.