Data validation list without duplicate entry

Dear Experts,

I want Data validation list which couldn't show duplicate value in entry please help. Example also in attached file.

Please try at
Data bank G2:K11
=INDEX(A:A,AGGREGATE(15,6,ROW(A$3:A$11)/ISNA(MATCH($A$3:$A$11,INDEX('Line 1'!$B$2:$E$10,MATCH(G$2,'Line 1'!$A$2:$A$10,),),)),ROWS(G$3:G3)))


Data validation list at
Line 1 B2
=OFFSET('Data Bank'!$F$2,1,MATCH($A2,'Data Bank'!$G$2:$K$2,),COUNT(INDEX('Data Bank'!$G$3:$K$11,,MATCH($A2,'Data Bank'!$G$2:$K$2,))))