Condtional formatting based on a letter being selected from 2 entered in another cell?

Hi there so weird question

I want to color code a cell yellow using conditional formating based on whether it matches the answer above. This is fine for me to do normally but today a weird one has come up where I need to be able to color a cell yellow if a letter from the cell above (which contains 2) is in the cell.

AD

A

B

D

C

In the table above the A cell and the D cell would both be yellow as A or D can be selected as defined in the header of the table data . is this possible using conditional formatting

Oh wow thanks so much this is amazing!!!