Use a ComboBox in your forms and every time you get a field entry that
is new, have VBA add it to a list and redefine your ListFillRange.

eg, a sheet called FormData to store the lists for the ComboBoxes or
other elements.
Column A has a list of Names used in ComboBox1

When the user clicks a button, SAVE or CONTINUE or whatever you have
at the end of your form, if ComboBox1.value is not in ColumnA then add
it to the bottom of the list, and update the ComboBox1.ListFillRange to
include the extra row. You could resort the list to if you want.