Script for adding together all measurements taken every hour

Hi there,

I have a rather unique problem. I have been making measurements for my research which are collected every hour and I am struggling to find a way to write a suitable script that recognizes the commencement of another hour of measurements and adds all the measurements together!
Basically I have two columns: On column states the time in 00:00:00 format, the other column is the measurement itself - any number at all. So several measurements are taken every hour:
For example,

Time Measurement
0:33:06 6
0:33:07 26
0:33:08 29
0:33:09 130
0:33:11 8
0:33:12 22
0:33:13 8
0:51:19 23
0:51:20 9
0:51:21 124
0:51:23 26
0:57:24 3
0:57:25 23
0:57:26 129
0:57:27 59
0:57:28 23
1:00:17 4
1:00:19 6
1:00:21 38
1:00:22 12
1:00:23 28
1:01:43 1
1:01:44 3
1:01:46 11
1:01:49 9
1:04:07 8
1:04:55 1
1:04:56 7
1:05:01 10
1:05:02 19
1:05:09 22
1:05:43 14
1:05:44 44
1:05:45 52
1:05:47 9
1:05:49 24
1:05:50 27
1:05:51 17
1:05:54 9
1:05:55 2
1:05:56 41
1:05:58 31
1:06:01 26
1:06:11 2
1:06:23 6
2:04:40 9

I would like to find a way to automatically add up only the measurements that occur across any given hour, so that I have a sum of all measurements across all hours in a day of measurements.
Any help at all is MUCH appreciated!

Thanks.