How to deduct the overlap time

[#1]

Hi,

The requirement is as follows

ABC100101	12/12/2011 1:27:33 PM	12/12/2011  4:05:28 PM	158
ABC100101	12/12/2011  3:43:58 PM	12/12/2011 4:06:13 PM	23
ABC100101	12/12/2011  4:30:45 AM	12/12/2011  4:44:44 AM	14

Duration in mins is

158 + 23 = 181 mins, but  what is  rquried is  (12/12/2011 1:27:33 PM) - (12/12/2011 4:06:13 PM) i.e  159  mins

Secon one 14 mins so 3hrs 14 mins

But what we require is

For first 2  it has calculate from 12/12/20111:27:33 PM to 12/12/2011 4:06:13 PM

Second one separately

Thanks

Venkatesh Salla