Hello Gary,
In the attachment you can find a sample project demonstrating your scenario.
The easiest approach to this task is to create an event in the UserControl.
In the event handler you can compare the UserControl that has raised the event and the content of the each TabItem. When they match, simply disable the TabItem.
The sample attached is pretty self-explanatory.
Another way is to add a public property to the UserControl which is of type RadTabItem. This property, however, can only be set in code-behind. So if you are creating TabItems dynamically, you can take the approach with the property.
If you have any additional questions or comments, contact us as soon as possible.
Greetings,
Kiril Stanoev
the Telerik team