This is a little tricky to explain, but hopefully will make sense.

A series of data is produced that monitors concurrent users on a
system. This is returned every five minutes of every day.
This is on a work book which has a month for each tab.

Data typically comes in the following, simple form:

Wed Nov 26 10:50:01 GMT 2008 0
Wed Nov 26 10:55:00 GMT 2008 0
Wed Nov 26 11:00:00 GMT 2008 1
Wed Nov 26 11:05:00 GMT 2008 1
Wed Nov 26 11:10:00 GMT 2008 1
Wed Nov 26 11:15:00 GMT 2008 1
Wed Nov 26 11:20:00 GMT 2008 1

Essentially, I need a way of differentiating between individual dates
and drawing out the highest value for each date. The dates are listed
in a long block and are already sorted, but need differentiating
between.

Er.. hopefully that's as clear as something thinner than mud.