Or....................
1] In B14, copied down :
=IFERROR(INDEX(LOOKUP(COLUMN(B$4:Q$4),COLUMN(B$4:Q$4)/(B$3:Q$3<>""),B$3:Q$3),AGGREGATE(15,6,COLUMN(B$4:Q$4)-COLUMN(A$4)/((B$4:Q$4/(INDEX(B$5:Q$10,MATCH(A$14,A$5:A$10,0),0)="x"))=C14),COUNTIF(C$14:C14,C14))),"")
2] In C14, copied down :
=IFERROR(AGGREGATE(14,6,B$4:Q$4/(INDEX(B$5:Q$10,MATCH(A$14,A$5:A$10,0),0)="x"),ROWS($1:1)),"")
Regards
Bosco