I need help with EXCEL formula

I am trying to customize my CSV in Excel for a CPA offer spread.

I have downloaded the CSV from network and need to subtract/divide the column that is currently containing my payout. I need to take the multiple each unique cell in the column so that my payout to my members is 50% less the total. Make sense???

Example: My payout in cell 1 = $1, My payout in cell 2 = $2

After formula..... Their Payout in cell 1 = $.50, Their Payout in cell 2 = $1

IS this possible to take an entire column of 3K offers with different # and have each cell uniquely divided on it's own?

Hope this makes sense! Thanks

Upload the CSV file to somewhere and I will take a look at it. That would be the best solution.