I have managed to do this with a slight hack. If you set the business start and end hours and the cell duration you can split the day into morning and afternoon.
BusinessBeginsHour = 9,
BusinessEndsHour = 18,
CellDuration = 240,
This will give you something that looks like:
12 | 16 | 12 | 16
but you can then use JQuery to find these values and replace them with your morning and afternoon text
$("[title='16 '] > div").text("Afternoon")