Extracting character embedded in a string

On the face of it, the following code will do what you want, but I'm wondering whether the codes can be any length and you'd like them truncated from the left to seven characters. I'm having some difficulty in working out more exactly what the problem is that you're wanting to solve. (this code doesn't exclude those lines that don't have eight consecutive numbers after the '?'. you'd do a LIKE with the same wildcard)

SELECT
  Stuff ( Clipped, PatIndex( '%?[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]%', Clipped ), 4,
         '#' )
FROM   ( SELECT
           rTrim( REPLACE( 'John Doe ?z1234563? Sally D ?1053442233?' + ' ', '? ', ' ' ) )
           AS
           Clipped )FirstPass 

-----------------------------------
John Doe ?z1234563 Sally D #3442233

You can do any pattern matching and replacement easy by CLR RegEx implementation.

You can take a look on the sample implementation SQL Server Regular Expressions – Replacements.

If I understand it exactly as @Magnus Ahlkvist in the comment, then using the above implementation, you can easily run below code:

SELECT
    AField,
    dbo.fn_RegExReplace(AField, '(.+?)(\?)(.+?)(\?)(.+?)(\?105)(.+?)(\?)', '$1$2$3$5#$7', 0) AS UpdatedField
FROM aTable

If you need other results, it's only a question of passing right Regular Expressions.