probably simple, but not for me, help please...

my parents have retired form the bakery, and now make product out of a
home bakey for homeless shelter at no charge. My mom wants to keep
track of everything that is made and subsequently given away. Column C
will be the stuff thats made while column D will be the give away.
What do I put in E to make it have a running balance. The dates will
vary depending on how much or how little is requested. I made a sampel
sheet to show you, and it is posted at; http://prodarts.homestead.com/bakerygiveawaysheet.html

thanks in advance for al your help