> automatically fill in today's date
This is the easy part, see http://www.filemaker.com/help/05-Create%20a%20database18.html.
Do the weekly weigh ins take place on a special day of the week or is everybody free to choose 'his/her' day of the week? Does it make sense to count the weeks from beginning of the year and store the number of the week in the record of weight record?
Everyone weighs the same day of the week. I hadn't thought about looking at it in terms of week number.
I've just downloaded your weightloser.zip and will go have a look at it. Thanks for your efforts. It's true a picture is worth a thousand words.