I don't think there is an automated way to do it. If there is it'ld be nice! But you can do by hand(you have ten fingers and ten toes!) seriously though...
format the time into the three parts hours:minutes:seconds
then plus/minus the two times and then use If's.
like:
If DifferenceTime < 0 then
Do
Minutes = Minutes - 1
While DiffernceTime < 0
End If
It works....

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DiGiTaIErRoR
VB, QBasic, Iptscrae, HTML
Quote: There are no stupid questions, just stupid people.