MSO 2003 Excel- need formula to sum "every 6th row" of "E column" 6782 + rows deep

The following formula was, several weeks ago, very graciously offered to me from one of Excel Forum's contributors.

=SUMPRODUCT(--(MOD(ROW(E8:E6782),2)=0),E8:E6782)

My request was to find a formula that would add each 6th row starting in row e8 (e8+e14+e20+e26+e32 etc. through e6782) in column "e" when the column was 6782 rows deep from top to bottom. (i am not trying to add every number in column e, just each 6th row, starting at e8 and going through row e6782).

I entered the formula into my spread sheet and, voila, I had a sum that I assumed was accurate for my spread sheet of ticket sales. I began to question the functionality of the formula when I altered the E8:E6782 parameters (which represented the gross ticket sales) to E4:E6778, in an effort to sum up the E4 values e4,e10,e16, e22,e28,etc. . . (which represents the net values after commissions were deducted). The difference in the two sums (e8 values Versus the e4 values) was incorrect and did not represent the appropriate commissions (which should have been 15%).

That formula is looking for every even row, as it is dividing the row number by 2. Try this one:

=SUMPRODUCT(--(MOD(ROW(E8:E6782)-8,6)=0),E8:E6782)

Hope this helps.

Pete