Thank you Mike.
Have you tried putting a line on the right side of each field (in layout mode)? Then match the right side of each field with the lines in your header.
The solution described in this link (which I found in Mike Mitchell's second link above) is probably what you need. A little bit fiddly to set up, but a lot less complicated than using field borders or hidden fields:
The trick (in FM12 and above) seems to be to make sure the vertical line does not touch the part above but DOES extend one pixel below the bottom of the part. Apparently in FM11 vertical lines did slide appropriately if drawn from top to bottom of the part, but the change in object position and size measurements from px to pt in version 12 broke this. The one pixel extension trick makes it work in 12 and above.
This is exactly what I did.
Thank you all for the help.
Thanks, Adam. Can you mark this as the "Correct Answer" so that others can find it?