Filling down in OO Calc

[Richard Beeston]

Hi all
Could anyone give me the instructions on how to fill down a formula in a column 
with increments for each row 
Formula example is
=SUM(D2:AM2) and I need to fill in 400 rows in a spreadsheet and put this 
formula in column C with an incremental formula going into each of the 400 rows.
I have tried to do this but the same formula has appeared in all the 400 rows 
without any increment and I do not want to have to redo each of the formulas 
row by row. 
Any help would be appreciated. 
thanks