How to copy the function SUM but offseted in 7 columns

[Leandro-Brazil]

I Have the folow situation :
The cells content is:
A1 = 50, B1 = 30, C1 = 40, D1 = 10, E1 = 20 and F1 = 10
Using the function SUM in the cell A4 = SUM(A1:C1) I have as a result 120
If I copy the cell A4 to B4 my SUM function will be B1 = SUM(B11) and the
result 80.
I would like to know how can I copy the SUM function from Cell A4 to B4 but
the SUM function should be SUM(D1:F1). And if a still copying to left side, I
mean to columns C, D, E... It should set the SUM functional to jump in each 4
Columns.
A4 = SUM(A1:C1), B4 should be sum D1:F1, C4 should be sum G1:I1 ...

Regards and thanks for your help

 

[Luke M]

Formula to sum A1:C1
=SUM(OFFSET($A$1,,(COLUMN(A1)-1)*3,,3))

Copying to the right will sum D1:F1, G1:I1, etc.

 

[David Biddulph]

= SUM(OFFSET($A1,0,3*(COLUMN()-1),1,3)) and copy across.