Right click on the graph and select Source data

after clicking in the data box, highlight the new range where the graph data
is on the spreadsheet. the graph should then get updated with the new set of
data. if you need to expand the range after every monht, the same process
can be adopted.

See if this serves your need.

"galatea2153" wrote:

Hi,
I prepare simple graphs each month for work. In the past I have simply
added a new column for new information, and (by clicking on graph and finding
the cells) expanding the graph to cover the new information. However, the
last couple of months when I click on the graph, no cells are highlighed and
I have to re-do the graph from scratch. I am unsure why this has happened,
seemingly for no reason. Can anyone give me any suggestions?