Hello Mark,

It is possible to achieve your scenario.

First of all, you need to create an event, set the EventType to Event and StartDate to any specific date you want to, such as following:

<Intersoft:UXCalendar HorizontalAlignment="Left" Margin="10,10,0,0" Name="uXCalendar1" VerticalAlignment="Top" CalendarDayButtonStyle="{StaticResource UXCalendarDayButtonStyle1}">
   <Intersoft:UXCalendar.Events>
      <Intersoft:UXCalendarEventItem StartDate="1/15/2011" />
      <Intersoft:UXCalendarEventItem StartDate="1/20/2011" />
   </Intersoft:UXCalendar.Events>
</Intersoft:UXCalendar>

Open your project using Microsoft Expression Blend. Right-click on the WebCalendar control and select Edit Additional Templates >> Edit CalendarDayButtonStyle >> Edit a Copy, then click OK.

Add the following code in the EventStates:

<VisualStateGroup x:Name="EventStates">
	<VisualState x:Name="HasEvent">
		<Storyboard>
			<ColorAnimation Duration="0" To="Red" Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)" Storyboard.TargetName="SelectedGlass"/>			
		</Storyboard>
	</VisualState>
	<VisualState x:Name="NoEvent"/>
</VisualStateGroup>

Attached is the sample file for your reference.

Hope this helps.

Thank you.