sumproduct multiple columns

[xahkazakhstan]

i have a data base with medicine and medical supplies in column 1 and unit prices in column 2.
the next 500+ columns are prescriptions per month.
I can calculate the price per prescription with 'sumproduct'.
but if i 'pull' this sumproduct of the first column of prescriptions over the next 500+ columns of prescriptions, the first array is not the price column but the adjacent, previous prescription column.
how can i get the price column as first array in a simple way?

[Kaper]

use dollar sign before letters of the column you want not to change during copying.
so instead of

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use

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it is called absolute adrressing (well in this case - mixed one). While normal mode is realtive.