Accessing sub-object properties in markup

[vpjoby]

I can see from other people's controls that it is possible to set sub-object properites in markup. For example, if I'm using Telerik's RadComboBox I can write ...\[code\]<telerik:RadComboBox runat="server" ID="RadComboBox2"> <CollapseAnimation Duration="100" /></telerik:RadComboBox>\[/code\]or, alternatively I can write...\[code\]<telerik:RadComboBox runat="server" ID="RadComboBox2" CollapseAnimation-Duration="100"></telerik:RadComboBox>\[/code\]What technique do I have to emply to allow me to do this with controls I write? I thought that I might have to explicitly create properties in my parent control for each of the of properties my sub-object I expose. However, I don't seem to allowed to create a property with a '-' in the name.