Compare 2 columns and conditionally format duplicates Excel 2007

[Anne Troy]

I would rather accomplish this with conditional formatting, but I am willing to do it with code.

The sample file is here: http://annetroy.com/ms/sample2columndupes.xlsx (what happened to being able to upload a workbook here? Hmmm.... anyway...)

I need to compare the values of the SET (both columns) of data in each row with the rest of the rows and highlight the duplicates.

Note that row 5 and row 6 are the same. Either the first record or second record or both should be formatted with red fill.
There is another set duplicated in rows 178 and 179.

I don't want to use a helper column. I know how to do that.

I thank you so much for your time. If you cannot understand my request, I will try to reword it.

 

[Weazel]

maybe something like...

=SUMPRODUCT(($M$2:$M$707=$M2)*($N$2:$N$707=$N2))>1

in the conditional formatting dialog box

 

[Anne Troy]

I can't tell if it works because so many cells are blank. Is there any way to add the condition that they're not blank? Thanks, Weazel!

 

[Weazel]

How about something like...?

=SUMPRODUCT(($L$2:$L$707=$L2)*($M$2:$M$707=$M2)*($L$2:$L$707<>"")*($M$2:$M$707<>""))>1

 

[Anne Troy]

Weazel, you are a God. Thank you soooo much!