I changed your references, change them back. I was playing with this, but I'm not sure what your expected answer would be...

=IF(ISERROR(OR(FIND("D",B3:B8,1)=0,FIND("D",C3:C8,1)=0)),"","D") (find() is case-sensitive)

If that isnt what you want, can you upload a sample workbook, showing your data (no sensitive info), and some sample answers?