Sum Formula
 

I would like to add a sum formula to a worksheet containing tabular numeric
data using VBA. I know that the sum formula for each row is @SUM(1,1:1,X).
How do I add the formula and do I have to do it for each row or can I copy it
and Excel will make the row number changes? I do not know the letter column
for the range but do know the numeric number. The amount of columns will vary
each time I run this macro. Thank you for any help you may offer me.