Outlook Forms - Calculating Time Spent At Work?

I am working on a form to calculate time spent at work, based on when the person started (8am), when they finish (5pm), and how long they have for lunch(1hour).  

I have my calculations to do work out the total time spent at work, however the difficulty comes with the time for lunch.  If a person decides to take only 30mins for lunch then their total time worked should increase, however I don't know what type/property to use for this?  Duration seems to just give hours, and modifying it in Date/Time means that 1:00 becomes 00:30 (half 12 at night).  It is all in the 24hour clock.

Does anybody know what I can use as the most appropriate type/property in order to subtract the time taken for lunch from the total hours worked?
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David LeeCommented:
Hi, angus_young_acdc.

I see two possibilities.  

1.  Use start and end date fields for lunch and calculate the time difference between them.
2.  Use a numeric field and use the DateAdd function to subtract the value entered in minutes.  For example

    WorkingTime = DateAdd("n", -NumericFieldName, RegularTime)
angus_young_acdcAuthor Commented:
Hi BlueDevilFan

Where would I declare the variable of WorkingTime?  Currently I am currently attempting validation inside a textbox control where it is equal to FinishTime - StartTime - LunchTimeTaken
David LeeCommented:
Are you using the "Calculate this formula automatically" option?  If so, then you should be able to code that in the formula box.
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angus_young_acdcAuthor Commented:
Yes I am.  When I change the Field to a custom one, in the textbox that I wish the value to appear I get the following error:
Error in Initial Value formula for "MondayDuration" -- Unknown field.

MondayDuration being the total time worked (end time - start time - lunch).
David LeeCommented:
Is MondayDuration a field (not a control, a field)?  If not, then the error is expected.  If end time, start time, and lunch are fields or the name of controls, then the calculation should read something like

    endtime - starttime - lunch
angus_young_acdcAuthor Commented:
Hi BlueDevilFan

In the Display tab of Properties it is listed as txtMondayDuration (so I'm guessing a control), and in the Value tab the field is MondayDuration of type Date/Time, format 12:37, property to use is Value.

However what you have suggested is already what is there, but will not meet the requirements.  The Lunch option is not a Date/Time it needs to be more numeric so that (for example) a value of 35 minutes could be entered for lunch and that value used in the subtract.  However I seem to be having problems with the conversion.

My reasoning for using Numeric is because if I enter 0:30 for the lunch duration, the controls display will change to 12:30.

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David LeeCommented:

Apologies for losing track of your question.  If you're still interested in pursuing an answer, then I'll be glad to get back to work on it.  If not, then I understand.  If you do decide to continue work on the question, then would you mind uploading a copy of the form so I can have a look at it?
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