You could have one form and two buttons - one button to show not departed and another to show departed.
Consider:
Click a command button, the following VBA code is executed:
Code:
DoCmd.OpenForm "frmPersons"
Forms "frmPersons" opens displaying all records.
Click button "Not Departed", sets a filter:
Code:
Me.Filter = "[DateDeparted] IS NULL"
Me.FilterOn = TRUE
Or click on button "Departed", sets a filter:
Code:
Me.Filter = "[DateDeparted] IS NOT NULL"
Me.FilterOn = TRUE
Third button ("Remove Filter") to remove filter
Code:
Me.Filter = ""
Me.FilterOn = FALSE