Selective masking in SQL server 2005

--Mask all but show only last 3 digits of the phone number
DECLARE @PhoneNo varchar(10), @Mask varchar(10)
SELECT @PhoneNo = '1234567890', @Mask = 'XXXXXXXXXX' 
 
SELECT @PhoneNo as 'Phone No', replace(@PhoneNo, substring(@PhoneNo, 1, len(@PhoneNo) - 3), 
substring(@Mask, 1, len(@PhoneNo) - 3)) as 'MaskedPhoneNumber'