VB.Net calculator code

I want to write a simple calculator program in VB.Net Later I will add more stuff to it. I have looked at 12 vb.net books and none explain how to enter number in a form text box then move that number to a storage area and subtotal display box. The subtotal box has to display a running total. Everthing I have tried to code wipes out the display box and shows only the current entry. Any ideas any good books ?