If I understand you properly, are you looking to sum the Total Cost by either Month, Desc and Actual Branch column?
If so, then you could use the SumIf function.
Lets assume that Months column is column A on row 3, and you wanted to sum the total for the GGN branch. You would enter the formula =SUMIF(O3:O8,"GGN",I3:I8) and would give the answer -5070.
Here is how the formula works (copied from the excel helpfile)
Range is the range of cells you want evaluated.
Criteria is the criteria in the form of a number, expression, or text that defines which cells will be added. For example, criteria can be expressed as 32, "32", ">32", "apples".
Sum_range are the actual cells to sum.
Hope this helps