property Schedule.HeaderAllDayEventHeight as Double
Specifies the height of the All-Day events being displayed on the control's All-Day header.

Double A double expression that indicates the height of the event to be shown in All-Day header. A positive value is multiplied with the font's height, while a negative value indicates a fixed height. For instance, 1 indicates that's the event's height is indicated by the control's font, while -20 indicates that the event's height is 20 pixels.
By default, the HeaderAllDayEventHeight property is 1, which indicates that the height of the event in the All-Day header is the same as the font's height. The HeaderAllDayEventHeight property specifies the height of the events to be displayed in the All-Day header. Use the ShowAllDayHeader property to show the All-Day header, so all All-Day events are displayed on this header instead in the time scale section of the schedule view. The AllDayEvent property indicates whether the event is an All-Day event. Use the Background(exScheduleEventContinuePrevWeek)/Background(exScheduleEventContinueNextWeek) property to specify an EBN object to be shown on the start/end of the week, if the event continues on multiple days.

The following screen shot shows the events in the All-Day header with the following EBN files:

The following screen shot shows the events in the All-Day header with no EBN files:

The following template x-script ( exhelper ), shows how to assign EBN appearance to events, including the next, prev signs:

OnResizeControl = 2048
ShowAllDayHeader = True
	SelectDate(#5/8/2012#) = True
	SelectDate(#5/15/2012#) = False
BodyEventBackColor = 0x1000000
Background(86) = 0x2000000
Background(85) = 0x3000000
HeaderAllDayEventHeight = -20
Events.Add(#5/8/2012#,#5/17/2012#).AllDayEvent = True