CALC problem

[Mike Shearer]

I have a spreadsheet containing information about events that occur at 
various times over two weeks.  I wish to sort the entries by the elapsed 
time in minutes between successive events.  A simplified example: column 
A and B contain the date and time when events occur, column C contains 
the calculated time delay between events using "=B2-B1" displayed as 
hour:minutes.  Column D calculates the time elapsed between events in 
minutes using "=HOUR(C2)*60+MINUTE(C2).  I want to "play" with the 
values in column D, such as sorting them and charting the results to 
highlight various characteristics of the original data.

How can I copy the calculated values from column D rather than take the 
formulae that determine the values?

Mike Shearer