Formula for SUM'ing by date/time

[gatorfan]

Hello All:
I need to come up with a formula in the Items at Risk box that will allow me to SUM the values in the Items Rem column of the sheet below based on the data in the Critical Time column. The sheet below is a small sampling of data that is exported from a web-based program numerous times/day to monitor performance. I don't want to overload you w/info you do not need so please advise as to any additional info I can provide.
Thanks in advance

Book1
	B	C	D	E
2	Items at Risk
3	11/18/2005	23:59
4	11/19/2005	6:00
5	11/19/2005	23:59
6
7
8
9
10	Critical Time	Processed	Total items	Items Rem.
11	11/18/2005 14:00	N	1600	1250
12	11/18/2005 14:00	N	2000	2000
13	11/18/2005 15:30	N	1100	984
14	11/18/2005 16:22	N	1250	856
15	11/18/2005 17:30	N	1600	1250
16	11/18/2005 21:00	N	1575	978
17	11/18/2005 23:59	N	926	560
18	11/18/2005 23:59	N	850	678
19	11/18/2005 23:59	N	2130	1608
20	11/19/2005 6:00	N	462	462
21	11/19/2005 6:00	N	1400	1400
22	11/19/2005 6:00	N	1625	1625
23	11/19/2005 6:00	N	950	950
24	11/19/2005 12:00	N	873	873
25	11/19/2005 13:30	N	1350	1350
26	11/19/2005 15:30	N	1675	1675
27	11/19/2005 23:59	N	2000	2000
28	11/19/2005 23:59	N	687	687
29	11/19/2005 23:59	N	356	356
Sheet1

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[Brian from Maui]

When you import the date/time are these true date/time values in Excel? If so, you can use a multi conditonal sum using Sumproduct. What are your criterias?