Calculate Hours

Hello, I need to have a macro/VBA that will do the following: For each date (Column B), search for an individual tag (Column D) and subtract the latest time stamp from the earliest time stamp (Ignore all the other timestamps). The Macro should be able to go over ~15,000 rows. There is about 15 dates and 50 individuals tags. For example: On the attached XLS, For 9/7/2012 and the tag number 22886 there are total of 5 timestamps.(Highlighted in Yellow) . The macro should take the latest time stamp for that date (18:27) and subtract the first time stamp of that date (10:01). Please note that the time stamps won’t be necessarily in ascending or descending order. The result will be 18:27-10:01= 8:26 The results should be placed different tab summarized. See also the attached xls. Thanks, Cooper