Calculate Multiple Percentages In Excel 2007

I have an Excel sheet that I use for my P & L statement.  I would like to calculate the percentage of revenue and cost on each line from my gross revenue.  It is a 12 month P & L with about 45 lines for each month that have cost and revenue numbers.  I need the percentage of gross sales for each line and the only way I know how to do it is to do each cell one by one.  45 x 13 (includes yearly as well) is just less than 600 cells I would have to do this for.  My question is, is there an easier way to do this.  If needed, I will attach a screenshot to better explain.  Thanks in advance for any help.
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I know you can make excel auto fill cells by selecting the cell at the top of this list and clicking the square in the corner and dragging vertically or horizontally. However this will move the cells that are referenced you can stop this with the $ wildcard.

eg. if i always wanted the cells to reference E3 i would write =$E$3

Hope this helps also if the cells were to be changed as u copied the information down the column it would just be =E3
It would help if you could post a sample sheet...

PCDOCAZAuthor Commented:
Onity, kind of makes sense, but not very savvy on Excel.. Only know basics, and will require more specifics.

Here is a blank sample sheet.  Looking to find the percentage of each revenue and cost column vs. total sales.
Unfortunately i do not know the calculation to be performed so i have just put =C10/C17, to copy missing ever other cell select the 2 columns and on the bottom right corner of the selected area there is a small square (circled in blue) click this and drag it out, when you release it the cells will be filled with the contents of the selected cells.

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PCDOCAZAuthor Commented:
Thanks man.. Perfect solution.  Made my life much easier!
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