lookup function with descending values vector

Is there a way to use the lookup function in reverse? The "lookup vector" on mine has to be descending, that is it it is a column going from high values at the top of the page to lower values at the bottom of the page. When using lookup function in this setup, excel gives me to wrong answer for some reason. If I make the lookup vector ascending, it works, but unfortunately the vector has to be descending in my worksheet....

Thank