Hi,
Try something like;
if (HasValue(startsamplingtime) and HasValue(endsamplingtime)) then
var millisecondsPerMinute = 1000 * 60;
var millisecondsPerHour = millisecondsPerMinute * 60;
var interval = Time2Num(endsamplingtime.formattedValue, "HH:MM:SS") - Time2Num(startsamplingtime.formattedValue, "HH:MM:SS");
// Calculate the hours, minutes, and seconds.
var hours = Floor(interval / millisecondsPerHour );
interval = interval - (hours * millisecondsPerHour );
var minutes = Floor(interval / millisecondsPerMinute );
interval = interval - (minutes * millisecondsPerMinute );
var seconds = Floor(interval / 1000 );
Concat( Format("Z9", hours), ":", Format("99",minutes), ":", Format("99", seconds))
endif
Regards
Bruce