Stock control spreadsheet

I thought I had posted this previously but ommited the subject and I don't
think it did post.

Although I have used Excel for years I have never had the need to use a
complicated formula.
I am trying to set up a stock control spreadsheet where multiple items are
deducted when I click on one cell.
What I am trying to do is each time I click on cell A3 "Item" all the
amounts in C will be deducted from D and the difference between B and D will
show in E


A B C D
E
1 Normal Amount In stock To
be
2 Stock level per item
ordered
3 "Item"
4 Side frame 200 4 200
0
5 Bottom bracket 100 2 100
0
6 Top bracket 100 2 100
0
7 Wheels 400 8 400
0
8 Axles 200 4 200
0
9 Springs 800 8 800
0
10 M5 Dome nuts 800 8 800
0
11 M4 Set screws 1600 32 1600 0

I don't know whether this is possible but if anybody has an answer (apart
from "your joking") it will be appreciated