生成 日期+随机不重複 4位数 (10984)

C2{=IF(A2="","",A2&TEXT(SMALL(IF(MMULT(N(IFERROR(TRANSPOSE(RIGHT(C$1:C1,4))-ROW($1:$9999),"")=0),ROW($1:1)^0)=0,ROW($1:$9999)),RANDBETWEEN(1,10000-ROW(A1))),"0000"))