I have a worksheet with 2 columns.

First column contains a date (several duplicates possible, even in hundreds).

Second column contains a code (4 or 5 different values).

Duplicates possible for first column + second column combination. For
example, for a given date, many records possible with same code value.

How could I write a formula to give me per code value the "unique" number of
dates found between 2 given date values. Meaning, as parameter I can pass
three arguments viz.
code value
start date value
end date value

In return I want the number of unique dates (including start and end date)
to be returned.

All help appreciated.