FINDB

Returns the starting position of a given text, using byte positions. FINDB is case sensitive.

FINDB(Find Text ; Text [; Position])

Find Text: The text or text expression to be found.

Text: the text in which the search is to be made.

Position: The position in the text where the search starts.

=FINDB("ａ"; "LibreOffice Ｃａｌｃ") returns 15. The Find Text argument is a text string that comprises a full-width, double-byte "a" character, while the Text argument comprises 12 single-byte characters followed by four full-width, double-byte characters.