I needed to create an IValueConverter in Silverlight and do to a Xaml binding conversion inside a ControlTemplate.
The solution is to do something like this:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:Hitachi.BusinessProcessViewer;assembly=Hitachi.BusinessProcessViewer">
...
...
...
<local:DateTimeConverter x:Key="DateTimeConverter"/>
...
...
...
<TextBlock DataContext="{TemplateBinding Created}" Text="{Binding Converter={StaticResource DateTimeConverter}}"/>
</ResourceDictionary>
...
...
...
}}