If your portal records have a date field, you can sort your portal (or its relationship) by the date field in descending order to put the most recent record at the top.
In FileMaker 11 only, you can define this portal filter expression:
Visits::DateField = get ( CurrentDate )
To only show portal records with today's date in the portal.
But you may want to try a different approach.
If you create a summary report on a layout based on visits, you can do a find for all records with today's date and list them in order with fields from the patients (and possibly the meds table) included on this layout to provide the complete info. The format of this report might lend itself to printing better than the data entry layout you show in your screen shot.