This is a question from How to count unique distinct records in a date range

Question: Is there anyway to do this based on date and another criteria? Say if C had dollar values and you wanted to only find uniques that were between a certain \$ value and a certain date?

Array formula in B35:

=SUM(IF(FREQUENCY(MATCH(IF((Date_rng<=Date_to)*(Date_rng>=Date_from)*(Amount_rng<=Amount_to)*(Amount_rng>=Amount_from), Text_rng, ""), IF((Date_rng<=Date_to)*(Date_rng>=Date_from)*(Amount_rng<=Amount_to)*(Amount_rng>=Amount_from), Text_rng, ""), 0), MATCH(IF((Date_rng<=Date_to)*(Date_rng>=Date_from)*(Amount_rng<=Amount_to)*(Amount_rng>=Amount_from), Text_rng, ""), IF((Date_rng<=Date_to)*(Date_rng>=Date_from)*(Amount_rng<=Amount_to)*(Amount_rng>=Amount_from), Text_rng, ""), 0))>0, 1, 0))-IF(ROWS(Date_rng)=SUM(IF((Date_rng<=Date_to)*(Date_rng>=Date_from)*(Amount_rng<=Amount_to)*(Amount_rng>=Amount_from), 1, 0)), 0, 1) + CTRL + SHIFT + ENTER

Named ranges
Date_rng (A2:A25)
Text_rng (B2:B25)
Amount_rng (C2:C25)
Date_from (B29)
Date_to (B30)
Amount_from (B32)
Amount_to (B33)
What is named ranges?

How to implement excel array formula to your excel sheet
Change named ranges.

Count unique distinct records in a date range and a numeric range.xls
(Excel 97-2003 Workbook *.xls)

Functions in this tutorial:

IF(logical_test;[value_if:true];[value_if_false])
Checks whether a condition is met, and returns one value if TRUE, and another value if FALSE

FREQUENCY(data_array, bins_array)
Calculates how often values occur within a range of values and then returns a vertical array of numbers having one more element than Bins_array.

SUM(number1,[number2],)
Adds all the numbers in a range of cells

MATCH(lookup_value;lookup_array; [match_type] Returns the relative position of an item in an array that matches a specified value

ROWS(array) returns the number of rows in a reference or an array

This blog article is one out of twelve articles on the same subject "count unique and unique distinct".