Another option using OFFSET() instead of Define Name.
1] A2, DataValidation formula :
=OFFSET($N$2,,,MATCH("zzz",N:N)-1)
2] B2, DataValidation formula :
=OFFSET($N$2,,MATCH($A2,$O$1:$Q$1,0),MATCH("zzz",O:O)-1)
3] C2, DataValidation formula :
=OFFSET($Q$2,,MATCH($A2,$R$1:$T$1,0),MATCH("zzz",R:R)-1)
All copied down
4] See attached file
Regards
Bosco