Here is the online version.
http://www.russellcottrell.com/VirtualYarrowStalks/VirtualYarrowStalks.htm#textLink1and the explanation.
The Virtual Yarrow Stalks I Ching works in the same way that conventional yarrow stalks do. You divide a virtual bundle of yarrow stalks to consult the I Ching, a volitional act similar to what you would do if you were holding real stalks in your hands.
Move your mouse over the stalks, then click on them to divide them into two “heaps.” The removal of one stalk and the counting through by fours of each heap is done automatically. Three such divisions determine one line, which is drawn beside the stalks. Repeat until the base hexagram is completed. If it contains moving lines, the transformed hexagram is displayed as well.
The earlier link is for the downloadable version, which can work offline.