To increment a formula reference by rows, when copying across columns you need a combination of the INDIRECT and ADDRESS Function. For example, place this formula in any row in Column "D".

=SUM(INDIRECT(ADDRESS(1,1)&":"&ADDRESS(COLUMN()-2,1)))

Now copy it across any amount of Columns. You will note that at each Column the row number increases by 1. In affect it will look like:

=SUM($A$1:$A$2) at Column D

=SUM($A$1:$A$3) at Column E

=SUM($A$1:$A$4) at Column F

=SUM($A$1:$A$5) at Column G

etc

The Syntax for the ADDRESS Function is

ADDRESS(row_num,column_num,abs_num,a1,sheet_text)

The last 3 arguments (abs_num,a1,sheet_text) are all optional. If your range resides on another sheet, it is the sheet_text that you need, eg

=SUM(INDIRECT(ADDRESS(1,1,,,"Sheet 2")&":"&ADDRESS(COLUMN()-2,1)))

Note that the Sheet name is supplied to the first ADDRESS function only