New Column with Time Scaled Values

Hi All,

In Excel 2007 sheet i have a column whose type is text. It contains date time stamp in chronological order but the difference of time between two adjacent rows is not same. What i mean is this:

Row1: 2011-01-21 09:17:33.0
Row2: 2011-01-21 09:18:33.0
Row3: 2011-01-21 09:27:33.0
Row4: 2011-01-21 09:29:33.0
Row5: 2011-01-21 09:33:33.0
Row6: 2011-01-21 09:38:33.0
Row7: 2011-01-21 09:47:33.0
Row8: 2011-01-21 09:51:33.0
Row9: 2011-01-21 09:60:33.0
Row10: 2011-01-21 09:66:33.0
....
...

The time difference between Row1 value and Row2 value is approx. 1min.
The time difference between Row2 value and Row3 value is approx. 9min.
The time difference between Row3 value and Row4 value is approx. 2min.
The time difference between Row4 value and Row5 value is approx. 4min.
so on...

Now i want a new coulmn that has following values in its rows:

Row1: 0
Row2: 1
Row3: 10
Row4: 12
Row5: 16
so on...

As you can see the values add-up in every next row.

Can anyone guide me how it can be done? Any help would be great.

-naeemdotcom