Column B contains primarily 4-digit numbers stored as text, with the balance of rows that are either blank or have a single word in the cell (I don't have control of how this data is entered, unfortunately). Column C contains initials + date, with some rows that include "N/A" at the end, as shown below:
MN–18 Jun 14
MC–16 Jun 14 N/A
AC–13 May 14
MN–25 May 14 N/A
I would like a formula that returns a count of the # of unique
4-digit characters in Column B for all the rows where Column C doesn't not contain "N/A".
I've attached a sample spreadsheet.