Decreasing and Increasing in excel 2007

Hi my name is blessedchild42

I have and excel assignment in which I have to manually decrease each of the six values in the sales amount column by $10,000.00 until the percent of quota sold in cell B14 is below, yet as close as possible to, 100%. All six values in column B must be increased the same number of time. The percent of quota sold in B14 should equal 99.85%. Can someone show me how to do this because I am confused.