MID("xx-xx-x-xx-aaa-aa-3", FIND("-", "xx-xx-x-xx-aaa-aa-3", FIND("-", "xx-xx-x-xx-aaa-aa-3", FIND("-", "xx-xx-x-xx-aaa-aa-3", FIND("-", "xx-xx-x-xx-aaa-aa-3") + 1) + 1) + 1) + 1, LEN("xx-xx-x-xx-aaa-aa-3"))
或
JOINARRAY(GREPARRAY(SPLIT("xx-xx-x-xx-aaa-aa-3", "-"),index>4), "-", 4)