實際交易月數 (13988)

F4{=SUM((A$2:A$21=E4)/COUNTIFS(A:A,A$2:A$21,B:B,B$2:B$21))

另解{=COUNT(MATCH(E4&COLUMN(A:L),A$2:A$31&B$2:B$31,))

另解{=COUNT(0/(MATCH(E4&B$2:B21,A:A&B:B,)=ROW($2:21)))