InfoPath Dev

Here is where I grabbed the code and setup the rules. http://www.bizsupportonline.net/infopath2007/calculate-date-difference-infopath-rules-formulas.htm

Do control V to paste.

If you go to the rule then action and click the fx button next to value you can paste the code. You need to make sure when you paste the code the field names match the fields in your form. If you haven't changed the names that I did you should be fine.

If you right click in that empty space and go to table properties. Make sure Row Height is set to "Automatically set row height".

I didn't create optional sections they are just regular sections that I labeled based off of the contents. I didn't create new fields I just cut and pasted your contents(tables) inside the section.

You're very welcome. Glad I could help.

If you click on each date picker and click at the top in the menu bar manage rules you will see how rules are made. I am attaching your form showing you how to hide sections so everything doesn't have to appear all at once or only appear when needed. If you look at the 3 sections for Authorized Driver Information, Company Vehicle, and ...

Please have a look at your form. I made the date diff function work for you. I edited the fields to startDate, endDate, and difference for simplicity.

Could you attach your form so I can have a look please. When you reply click options and upload your form.

I am attaching a form which should demonstrate what you are trying to do.