I think the "SUMPRODUCT" function would work for what you want.
Let's say the "Charge out rate" is in column D and month 1 is in column E. Let's also say you have data in rows 5 to 10.
Your formula for the total for month 1 would be:
Code:
=SUMPRODUCT(D5:D10, E5:E10)
This should provide the required total.
You'd need to adjust that slightly as if you just copy it for months 2 to 12, the references would change. So:
Code:
=SUMPRODUCT($D$5:$D$10, E5:E10)
This will force it to use the data in the charge out rate column for the first range.
You then need to change this once more to accommodate you adding and removing rows from the spreadsheet. The "INDIRECT" function would do this, and would also help with your original question.
You could use this with "SUMPRODUCT", together with the "ROW" and "COLUMN" functions. For example:
Code:
=SUMPRODUCT(INDIRECT("r5c4:r" & ROW()−1 & "C4",FALSE), INDIRECT("r5c" & COLUMN() & ":r" & ROW()−1 & "C" & COLUMN(),FALSE))
Here, "INDIRECT" is using what's known as "RC" cell references. For example, "r5c4" is row 5, column 4, i.e. cell D5. You'll need to update these numbers for your own spreadsheet.