Questions about Formula in Excel

Hello,
I have a query about Excel. How can I receive a column (bar chart) which will include variables as a sum?
For example: I have variables: A and B. A =20% and B=40%. I require a column which will depict the sum of these variables (60%). But I require in the column to be obvious that from the 60% the 20% comes from variable A and the 40% from variable B. So, the Column ought to be divided in two parts (in proportion).
Lots of thanks.
