Time Problem

I'm wondering why you just want to display Hours Worked as a Date. In this case, you could just add an End Date field ;-)

If you really want to calculate the exact hours worked - you must also know the End Date. So like kine wrote, you should add an End Date field or you could also use DateTime as date type. In this way you should only have one field for Start Date and one for End Date.

Ex.

Variable:
StartDateTime : DataType DateTime
EndDateTime   : DateType DateTime
HoursWorked   : Integer

When inserting in the Attendence table:

Attendence.StartDateTime := CURRENTDATETIME;
Attendence.INSERT;

On the Validate Trigger for EndDateTime add:

HoursWorked := (EndDateTime - StartDateTime) DIV 3600000; 

(EndDateTime - StartDateTime) is in milliseconds, so to get hours with have to do a division with first 1000 (=seconds), then with 60 (=minutes) and then with 60 (=hours). 

So when you now add the EndDateTime, HoursWorked will be calculated automatically:

Attendence.VALIDATE(EndDateTime, CURRENTDATETIME);
Attendence.MODIFY(TRUE); 

In case you would like to keep 2 fields per Start and End, you can still use the above example. Just change the HoursWorked calculation to the following:

StartDateTime := CREATEDATETIME(StartDate, StartTime);
EndDateTime := CREATEDATETIME(EndDate, EndTime);
HoursWorked := (EndDateTime - StartDateTime) DIV 3600000;

Yes - Duration is also a great idea.

Just notice, that you then will have the value in the following format: "13 hours 21 minutes 55 seconds 781 milliseconds"

Depending on what you would like to use the result for - you can either use Duration or calculate HoursWorked by yourself.
My example calculates whole hours, which means that HoursWorked will be 13 and not "13 hours 21 minutes 55 seconds 781 milliseconds".

(If you like to have the decimals, then exchange DIV with / ;-) )

"Total Hours" should be Duration.

But remember, that if you choose to use duration - you must use DateTime variables to calculate the duration.

Check out Help (F1) ;-)

Use this data type to represent the difference between two datetimes, in milliseconds.
This value can be negative. It is a 64 bit integer.

DATETIME-DATETIME=DURATION