How can I change/update editmask in runtime?  

I have a class like that:

public class Customers : BaseObject
    {
        public Customers(Session session)
            : base(session)
        {
        }

        private Countries counties;
        public Countries Countries
        {
            get
            {
                return counties;
            }
            set
            {
                counties = value;
                OnChanged("Countries");
            }
        }
        private string customerName;
        public string CustomerName
        {
            get
            {
                return customerName;
            }
            set
            {
                customerName = value;
                OnChanged("CustomerName");
            }
        }
        private string customerPhone;
        public string CustomerPhone
        {
            get
            {
                return customerPhone;
            }
            set
            {
                customerPhone = value;
                OnChanged("CustomerPhone");
            }
        }
    }
    public enum Countries {
        Australia,
        Brazil,
        Russia
    }
 

When i choose in combobox Australia,I want to set (00)0000 0000 in EditMask of CustomerPhone.
If I choose Russia , I want to set (99)000 000 000 like that
How can i do it in runtime?

This approach works when using in the Win app. Is there a possibility to change the code so it works for both Win & Web ? I'd like to put as much code as possible in the App.Module.

Greetings
Xavier