3 drop-down lists and lookup value

[PE2009]

I have 3 drop down lists shaded in green. I want to choose a Hydrologic Soil Group from a drop-down list. I want to choose a Cover Type from a drop-down list. Finally, I want to choose a Cover Description from a drop-down list. All lists have already been created and work fine. The problem is....

In the red shaded cell L9 I want an equation that will look up a Cover Type (D9), Cover Description (D10) and a Hydrologic Soil Group (C9) and return a CN value from the table in the CN Values worksheet. If the soil group is A the the CN value should be 57. B returns 72, C returns 81, and D returns 86.

I would appreciate any help on this.