How dynamically set validation attributes to a Model MVC 2?

Question

Lets says I have the following model

public class Person 
{
  [NameIsValid]
  public string Name { get; set;}
  public string LastName { get; set; }

}

I created a custom attribute NameIsValid for this model. Lets says for ViewA I need the custom attribute validation in the model, but for ViewB I dont need this custom validation attribute, how can I dinamically set or remove the custom attribute from the model when need it?

Thanks!