dependency issue, need workaround

Hi everyone,

My formula has dependency issue but somewhat the value need to be changed depending out the output

On sheet 2 -- table organic -- F14 is where the error lies

On sheet 2 -- table index: this is where the assumption of rising cost based on certain number of app install cumulative (sheet 1 -- column P)

Is there any solution on this?

Warm regards,
Fanie