DataGridView - Intercepting the adding of rows

I see the DataGridView control has a property "AllowUserToAddRows" that I can turn on or off but what if I want the ability to be context dependent.

i.e. I want an event that will fire when the user attempts to add a row in which I can cancel if certain conditions aren't met but I can't find an appropriate event.

Any ideas on how to do this?

Check out Beth Massi example for your issue where she does validation for adding and editing using a partial class to a dataset to enforce validation rules.

http://msdn.microsoft.com/en-us/vbasic/bb643821.aspx