Auto complete formulas horizontally

Looking for some help..

Is there any way Excel can auto complete formulas horizontally?

Say i want to show the sum of a coloumn on the bottom row. How can i do this without having to drag the formula 300 cells??

When the issue is vertically, one can just double click in the low right corner of the first cell.

Did you guys understand my question?? Hope you did!

Thanx for any answer!

Say you have a formula in column A and you want to fill across 300 columns then type the range into the box above cell A1, e.g. if you have a formula in A100 and you want to fill across to KN100 then type in the range

A100:KN100

Press ENTER so that the whole range is selected then, on the Home tab at the right hand side, select "Fill" and "Right"

Thanx!