Just to offer an explanation of why Wayne's solution is the correct one,
Access only recognizes Times as part of a timestamp (i.e.: in conjunction
with a date). This is due to how Access stores date/time values: they're 8
byte floating point numbers, where the integer part represents the date as
the number of days relative to 30 Dec, 1899, and the decimal part represents
the time as a fraction of a day (for example, 6:00 AM will be .25, noon will
be .5, 3:00 AM will be .125, 8:00 AM will be .3333 and so on) If you store
just a time, since the integer part is 0, Access is actually treating the
time as being on 30 Dec, 1899. (It's easy to prove this: simply format your
time as Format(MyTimeValue, "yyyy-mm-dd hh:nn:ss"))
Since they're just numbers, you can add the times together, but as soon as
the sum exceeds 1, you "lose" 24 hours from your total: rather than 6:00 +
8:00 + 6:00 + 7:00 = 27:00, you'll get 3:00 (on 31 Dec, 1899)
HTH