Need help removing duplicate entries wihtin 30 minutes of each other.

New to the forums, and have a headache I need help with.

I have a spreadsheet with these columns:

A: Customer ID (9 or 10 digit numeric)
B: User ID (7 digit alpha numberic)
C: Created (mm/dd/yy hh:mm:ss)

Example:

Customer ID User ID Created
123456789 U11U11 04/11/2012 02:35:43
123456789 U11U11 04/11/2012 02:35:56
1123456789 X11X11 04/12/2012 08:52:12
1123456789 X11X11 04/12/2012 08:54:13
1123456789 X11X11 04/12/2012 08:59:12
2123456789 X11X11 04/12/2012 09:01:45
2123456789 T11T11 04/12/2012 09:52:55
2123456789 X11X11 04/13/2012 12:15:22
2123456789 X11X11 04/13/2012 12:18:22
2123456789 T11T11 04/13/2012 01:18:25
1234567890 T11T11 04/13/2012 02:25:54
4123456789 J11J11 04/14/2012 17:55:29
4123456789 J11J11 04/14/2012 18:01:42
4123456789 J11J11 04/14/2012 18:02:36


What I need to do, is filter out all of the timestamps by the same User ID, to the same Customer ID, that are within 30 minutes of each other. So in the above example, it would end up as:

Customer ID User ID Created
123456789 U11U11 04/11/2012 02:35:43
1123456789 X11X11 04/12/2012 08:52:12
2123456789 T11T11 04/12/2012 09:52:55
2123456789 X11X11 04/13/2012 12:15:22
2123456789 T11T11 04/13/2012 01:18:25
1234567890 T11T11 04/13/2012 02:25:54
4123456789 J11J11 04/14/2012 17:55:29


Anyone have any ideas? I found something about adding a helper column on the web from 2004, but it is not working for me with the formula provided (found here http://www.mrexcel.com/forum/showthread.php?t=346085 )

Any help would be greatly appreciated!

Here is a sample with the above data.