set the style for items only in current month

[Zhong]

I want to change the background of each CalendarButton item in the current month, but for those items not in current month (some days from previous month or next month) I want to change them to another background. right now, if I add the ItemTemplate, all items background will be changed. How can I set the background for those different types items?
Many thanks!

[Zhong]

I found the property "IsFromCurrentView", it solved my problem. Thanks

[Alex]

There is a visual state in the 
 <Style x:Key="CalendarButtonStyle" TargetType="calendar:CalendarButton">
....
    <VisualState x:Name="IsNotFromCurrentView">
.....

Use it