SSRS Report Properties Code

I am using the below Code to bring back any number that start with SS, if they are Null or do not start with SS I would like to bring back N .  I am having trouble with the, or SSNumber <> "SS*".

public function SSNumberPicker(SSNumber as String)as String

if SSNumber is System.DBNull.Value or SSNumber =  ""or SSNumber <> "SS*" then

SSNumberPicker="N"

else

SSNumberPicker=RIGHT(SSNumber,(LEN(SSNumber)-4))

end if

end function

Thank you