To get result set where Company field value lays between Edit1 and Edit2:
with Customer do
begin
EditRangeStart;
FieldByName('Company').AsString := Edit1.Text;
//Set start range based on text of Edit1 component
EditRangeEnd;
FieldByName('Company').AsString := Edit2.Text;
// Set end range based on value of Edit2 component
ApplyRange; // Apply the ranges
end;