Detect duplicates

Can somebody help me with this quite complicated problem. I need to detect duplicate row in excel, i cant use "Remove duplicate" function because I want to see what are duplicates.

*Every row has got 4 cells.
*I have got around 50k rows which have do be process
*Those rows which are duplicates must be marked with numbers 1 2 3 etc.
*Complicated problem: Column A and B has got coordinates which may vary around +- 0.001

There a picture to imagine what i need:
3 rows.png

Ask questions, maybe i didn't explained the problem clearly.

please do not post images for worksheet calculation/formula problems
Attach a sample workbook. Make sure there is just enough data to make it clear what is needed. Include BEFORE/AFTER sheets if needed to show the process you're trying to complete or automate. Remember to desensitize the data.

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=COUNTIFS($B$2:$B$22, $B2, $D$2:$D$22, $D2)>1

Range = $B$2:$B$22
Starting cell = $B2
Condition= ">1" meaning the condition is met if there is more than one set of data that have identical character or data sequence.

Note the "$B2" is not "B2" because it need "$B" needs to stay the same, while "2" will change.

That is the formula I used. It checks the First and Last Name column for duplicates and uses conditional highlighting to highlight the first name if of the contact if its a duplicate. You can modify it to include other columns using http://office.microsoft.com/en-us/ex...005209029.aspx as a reference. You will use the formula above, but change the column (ex. $B will be $A) and the number of rows per column.