Put this in A2 and copy down:
=SUM(OFFSET(Sheet1!$A$1,100*(ROW()-1),0,100,1))



Joey wrote:

Example sheet 1
a1 to a1000 each has a different number:
sheet 2
cell a1 add sheet 1 a1 to a100
cell a2 add sheet 1 a101 to 200
Is there a way to copy formula into cell a3 without editing it.

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Dave Peterson