CREATE VIEW dbo.your_view
  AS
SELECT ClientName
     , MembershipNo
     , RegistrationDate
     , YearsRegisteredFor
     , DateAdd(yy, YearsRegisteredFor, RegistrationDate) As ExpiryDate
     , DateAdd(dd, -7, DateAdd(yy, YearsRegisteredFor, RegistrationDate)) As A_WeekB4Expiry
FROM   dbo.your_table
GO

SELECT ClientName
     , MembershipNo
     , RegistrationDate
     , YearsRegisteredFor
     , ExpiryDate
     , WeekB4Expiry
FROM   dbo.your_view