See if one of these works for you

This one uses only A1:B12
=SUMPRODUCT(A1:A12,B1:B12)

or
This one just includes a larger range than you need
=SUMPRODUCT(A1:A100,B1:B100)

or

This one automatically adjusts to additional data (no blanks, though)
=SUMPRODUCT($A$1:INDEX($A:$A,MAX(COUNT(A:A),COUNT( B:B))),$B$1:INDEX($B:$B,MAX(COUNT(A:A),COUNT(B:B)) ))

or
This one allows for blanks between the number entries and uses the range
that includes the last numeric entry in Cols A or B
=SUMPRODUCT($A$1:INDEX($A:$A,MAX(MATCH(10^99,A:A), MATCH(10^99,B:B))),$B$1:INDEX($B:$B,MAX(MATCH(10^9 9,A:A),MATCH(10^99,B:B))))

Does that help?
***********
Regards,
Ron

XL2002, WinXP


"holly" wrote:

i know i have done an easy formula in the past where i can add new rows and
not have to re-do the forumla to sum an example like a1*b1 through to
a12*b12. does anyone remember how to do this without having to ancor colum a
row by row?