──LASTPOS(needle,haystack──┬─────────┬─)─────
└─,start──┘
LASTPOS returns the position of the last occurrence of one string, needle, in another, haystack. If the string needle is not found, 0 is returned. By default the search starts at the last character of haystack (that is, start=LENGTH(string)) and scans backwards. You can override this by specifying start, as the point at which the backward scan starts. start must be a positive whole number, and defaults to LENGTH(string) if larger than that value.
Here are some examples:
LASTPOS(' ','abc def ghi') -> 8
LASTPOS(' ','abcdefghi') -> 0
LASTPOS(' ','abc def ghi',7) -> 4