Client-side you just need to add the desired selector to your table. In example, add a selector to a javascript (sorry I have no experience on the .NET side btw it will not differ a lot) table is made with one line of code:
Code:
myTable.setSelector("This is my selector");
Server-side you must implement the selector's logic inside the metadata adapter.
You must develop your own MetaDataProvider and implement both isSelectorAllowed and isSelected methods.
The first method will decide if a specified selector is allowed for the specified user on the specfied item, while the second method lets you filter updates on a selector-basis.

Hope that helps,
Bye.