Overtime Query

[Drum2001]

I have designed a "Time Tracker Database"... Basically a Time Clock. I

have report that calculates the number of regular hours worked per
week.

Currently I am running the following query:
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SELECT DateFilter.Employee, DateFilter.TimeTypeIn,
Sum(DateDiff("s",[ClockIn],[ClockOut]))\3600 &
Format((Sum(DateDiff("s",[ClockIn],[ClockOut])) Mod
3600)/86400,":nn:ss") AS TotalTime
FROM DateFilter
GROUP BY DateFilter.Employee, DateFilter.TimeTypeIn
HAVING (((DateFilter.TimeTypeIn)="Regular"));

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This works great, and returns the total time. Now, what I would like
to do is calculate overtime. So basically I want:

TotalTime - 40 hours = Overtime

TotalTime would be calculated with the DateDiff above...

Any suggestions to accomplish this?