thanks for all of the suggestions.
ended up it was simpler than i thought.

access does actually increment above the 24hours, but it adds days to a date, so to get the actual hours i wanted i divided it by 24, put this into another text box overlapping the actual time it was showing as the minutes and seconds were always correct.

VB Code:
  1. DatePart("h",Sum([TimeField]))/24

there were a couple of variations needed on the form to ensure it was correct, but that is the main part of it.

Thanks again