I'm going to have a hard time explaining what exactly I am trying to do.

I am creating a log of vehicle registrations, it includes a plate#, state,
VIN, and the date when I recieved the registration and title. I have the info
sorted by plate#. What I am trying to do is create a drop down menu for the
date. I only want the info showing that has no date input but in the dropdown
menu can bring up either every entry or just particular dates. Everytime I
enter a date I want it to be automatically entered into my drop down menu. I
have had this before but it had been set up for me at my last job but am
completely clueless on how to do it myself.

I assume there needs to be a entry in the drop down menu of; all, blanks,
and somehow every date that I enter that should automatically be entered into
the dropdown menu.

If anyone has any idea, particularly a step by step how to it would be
greatly appreciated.