Yes.
You'll have a table for data entry, which is designed so, that it is easy to make various calculations. The best way for this is to try to design this table as database-like as possible.
For graph, you design a table which is easy to read for graph. And all (or most) data there are read form data entry table.

When I remember correctly (I don't have Excel available at moment), company names are on both data entry and report sheets entered manually (selected from data validation lists). It is possible to read companies into report table, but this is much more complicated. The question was about graph creating, not about calculations using hidden tables and hidden columns to get a list of companies :-)