Put the following code in the AfterUpdate event of your control:
Me!NameOfYourControl.DefaultValue = Me!NameOfYourControl

The control will "remember" the last entry for as long as the form is open
but "memory" will be lost when the form is closed.

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Fletcher,
  I think what you're referring to is the ability to make a bound control
assume a DefaultValue during an entry/editing "session".
  Let's say you have a field called City, and the next 20 records you want
to add are all "Boston" for the City value.
  Use the AfterUpdate event of City to set a DefaultValue for City.  (Enter
Boston as the City)

       Private Sub City_AfterUpdate()
           Me.City.DefaultValue = "'" & City & "'"
       End If

  Every New record you add during that session will have a City
DefaultValue of "Boston"...
  UNTIL... you change it to something else.
  After 20 Boston records, you enter a "New York" record... now... "New
York" becomes the DefaultValue, and any new records, from then on, will have
a City value of "New York"

  This is only in effect for the current "session" of that form.

Fletcher,
  For clarity, I'll expand the quotes in the code I suggested, so you can
it more clearly.
  Do not use the spaces in the real code...
           Me.City.DefaultValue = " ' " & City & " ' "