Counting unique column entries while also meeting other criteria

I have a very large worksheet which grows daily. I want to count the unique entries residing in column L (containing model numbers) which also meet certain criteria. I have successfully counted those entries meeting the criteria using:
=COUNTIFS(Quotes!$L:$L,"<>DELETED",Quotes!$J:$J,">="&A3,Quotes!$J:$J,"<="&$B3,Quotes!$O:$O,"<=1000000")

Where the entries in column J are dates and the entries in column O are dollar values. A3 and B3 are also dates.

This is great, but it doesn't give me the number of unique entries. I tried the Sumproduct/Countif expression I found elsewhere, but it doesn't work.
The data in column L is formated as text and entries look like this:
DELETED
DELETED
DELETED
6811
10078-63/75
X82
10078-63/75
10078-63/75
10078-63/75
10078-63/75
10052
10052
10052
X81
X17
X14
X6
X5
X5
X29
6838

Is this possible? I am using Excel 2007.