Building a Time Card

Unfortunately, what you are asking for is beyond just a simple customization and as such, I can only point you in the right direction on a few things. If you want to hire someone to develop this, then you'll want to post in our Job Board - http://www.gravityhelp.com/forums/forum/job-board

To start with Gravity Forms doesn't support reviewing submitted information before creating a post. So the easiest way to do what you ask is to create two forms. One to input information and using the redirect with Pass Field Data Via Query String to move the information submitted to the next form which will display it.

On either the first form or the second form after it is submitted, or on the second form, before things are displayed, you'll need to do your time calculations. You'll have to write a PHP function in your functions.php file to grab the relevant details and do the calculations based on your criteria. Then pre-populate fields based on the result.

Here's a forum thread on reviewing data before submission:
http://www.gravityhelp.com/forums/topic/review-data-before-submiting

Finally, your user can then click submit once again, and all of that data will be saved to the form. You could then export the entries on the second form and get everything you need to track time.

Using the Gform_post_paging doesn't really allow you to easily grab field information from a previous field, and the HTML block doesn't automatically pull from previously entered fields either, which is why you don't see merge tags for fields listed in the drop down. You can do this through short codes as long as the data has been submitted from a previous form like I mentioned above.

Check out this example:
http://www.gravityhelp.com/forums/topic/inserting-passed-query-string-values-into-an-html-block

Hope this all helps.