Programmer's should find this easy to understand! As you specialize cells they become harder to change. Just like if you had one ancestor class that had been inherited over and over from subsequent generations of child classes. If you're an class at youngest leaf of this inheritance tree, then it very difficult to look and act like another leaf at the other side of the tree which has followed a completely different inheritance path. So when each of us starts out as a newly fertilized egg, we are a wee bag of cells that can be anything. However every time a cell splits, its child cells become a little bit more like a blood cell or a bone cell. And these similar cells hang around together creating more and more specialized versions of themselves. My biology isn't great, but I believe creatures that can regenerate have super-cool highly specialized cells that can create new similar cells. Us humans lost the the ability to do that millions of years ago as evolution decided it was worth the effort creating these cells. Probably because by the time a new leg had grown back, you'd already have been eaten by a sabre-tooth tiger!! HTH gogza

And quad-core processors! gogza

In that case use VB! ;) Instantally more readable and accessable! gogza