excel forward backward seq

B2=INPUT
B3 =INDEX(A1:G1, MOD(MATCH(B2, A1:G1, 0), COLUMNS(A1:G1)) + 1)

B4=INDEX(A1:G1, IF(MATCH(B2, A1:G1, 0)=1, COLUMNS(A1:G1), MATCH(B2, A1:G1, 0)-1))