help with a complicated find and replace

The problem is that I don't want to change the second part of the reference (which goes backwards and is fixed on row 6).

For how many columns backwards in row 6 does this go?

With the understanding that they go all the way back to column A (15 columns) try this formula and fill down.

Formula:

=O20*INDEX($A$6:$O$6,1,MOD(-ROWS($1:1),15)+1)