depends on how you want to use it...if you only want to display the record associated with the earliest date, I would set a variable in the group header and then suppress all detail records that don't match...
in the header
global datevar earliest := {table.datefield};
"" //to hide the assignment (or don't use and place on the form where the date would be displayed)
in the Section Expert for the detail section:
global datevar earliest;
earliest <> {table.datefield}
Hope this points you a direction that'll work for you