reference date above last cell in range displaying "1" or "2"

[leeroyrooney]

I have a range d20:ah20 when via dropdown box you can select either A,B or C.
(If c is selected nothing should happen only a & b require calculation-the data may show a mixture a,a,a,b or a,c,c,c,c,b or c,c,c,c,c (if all ccccc the date in the celll should not change)
In range d6:ah6 it displays 1st,2nd,3rd etc. to represent the date of the last A or B.
The data is printed and deleted monthly so i need a macro to check the range d20:ah20 for the last A or B and return the date in corresponding column in the range d6:ah6 in cell AR5