I am guessing that you want to chart (graph) the positive and negative values.
If your data is in the range A1 to E3,
with headings on row 1
positive readings on row 2
and negative readings on row 3
with series labels in column A,
select all the range A1 to E3 and select Insert - Chart
(I don't have Excel 2007 on this PC, so I can't give you the exact steps from the Ribbon)
From the Column group of charts select Stacked column
Include chart title and axis labels as required and click Finish.
On the new chart (graph):
Right-click the Value axis and select Format axis ...
In the Scale Tab, set the minimum value to say -0.01
Then in the 'Category (X) axis crosses at' box, enter the same value (-0.01)
Set the maximum value to the same but positive value +0.01
You now have a chart (graph) displaying the positive and negative values for each month.
Hope this is what you were looking for - if not please provide more details.