Question : MS SQL count total time.

I have a database like the excel file below, I want to count total time which value < 400, please help me this problem, thanks!
Time(varchar)
Value: int

Time      Value
3:39:35      429
3:39:40      433
3:39:45      438
3:39:50      443
3:39:55      399
3:40:00      300
3:40:05      453
3:40:10      455
3:40:15      457
3:40:20      398
3:40:25      460
3:40:30      460

--> like the data above, total time < 400 is:  (3:40:05 - 3:39:50) + (3:40:25 - 3:40:15)

Answer : MS SQL count total time.

I would not install BES on that server. You are already going againist Microsoft Best Practices by running exchange on a dc. I would definetly run it on a secondary machine.