Graph and updating
 

I have a real problem that is doing my head in!
I have a sheet that is filled in every week with figures from 45 different
companies - each company has a line with, say, column C being the input
column which then works out the amount minus VAT and places it in column D.
What my client wants is for that info then to be transferred to a graph that
updates itself every week when new figures are inserted. Is this at all
possible and if so, how on earth do I do it?
Just to qualify the above:
The figures are inserted into Sheet1 (called Workout) and then every week
they are overwritten with the new figures but the client wants the figures
updated every week on Sheet 2 (called Graph), showing the trend of the sales
for each company.

Hope someone can help me with this

Nick