Loop equation till reach needed meaning

Hello everyone,

Could some one help me to create loop, that could make something like this:
I have in cell (D;7) minimal efficiency for example 80 %.
In (H;10) cell there is calculated effectiveness which depends on the RPM number. (effectiveness = -0,0048*(rpm^2)+0,2344*(rmp)+100)
(D;10) RPM number.

By using equation mentioned above we get some efficiency for certain RPM:
RPM = 160, E = 14,62%
RPM = 150, E = 27,16%
RPM = 140, E = 38,74%
RPM = 130, E = 49,35%
RPM = 120, E = 59,01%
RPM = 110, E = 67,70%
RPM = 100, E = 75,44%
RPM = 90, E = 82,22%
RPM = 80, E = 88,03%
RPM = 70, E = 92,89%
RPM = 60, E = 96,78%
RPM = 50, E = 99,72%

Is it possible to create a loop, which will reduce RPM amount from 160 by 1, till effeciency will be not less than set in (D;7) cell.

If minimal efficiency > calculated efficiency, than RPM-1
If minimal efficiency <= calculated efficiency, than show this RPM amount in (D;10) cell.

Hope so than someone will understand what im trying to say