excel formulat charactes at nth poistion are from a list of allowed characters code example

Example: excel formula find 2nd occurrence in string

To find the 2nd backslash in the text in cell A1:
=SEARCH("^", SUBSTITUTE(A1, "\","^",2))

To find the 4th period in the text in cell A1:
=SEARCH("^", SUBSTITUTE(A1, ".","^",4))