Hello Donald,
=IFERROR(IF(B6="",C5,IF(MID(B6,(FIND("-",B6)+2),3)*1=20,MID(B6,(FIND("-",B6)+2),4),IFERROR((MID(B6,(FIND("F",B6)-4),4))*1,(MID(B6,(FIND("A",B6)+1),3))*1))),IFERROR((MID(B6,(FIND("F",B6)-4),4))*1,(MID(B6,(FIND("A",B6)+1),3))*1))
This seems to work for the data that you gave.
Regards
Harry