I have data as follows

A1=00:00:30 (representing a counter 00 hours 00 minutes 37 seconds)

B1=00:00:45 (representing a counter 00 hours 00 minutes 42 seconds)

C1=00:01:00

The cells are formatted as hh:mm:ss

i need a macro that will add a certain time interval (positive or negative)
to A1 (via inputbox) e.g +31 seconds
and each subsequent time interval increases or decreases by this amount.
If 31 seconds is inputed

A1 will read "00:01:01"
B1 will read "00:01:16" and
C1 will read "00:01:31"

is there a simple macro that can do this, or will i have to write a long
macro looking at each seperat component i.e hh then mm then ss and using
lots of if s%60, and if m%60 and if h%60 etc etc.....


Sunil