Simulink : how to make run a switch/case inside a block "Matlab function" ?

Hi,

I have a little problem with Simulink concerning a switch/case structure. In a block Matlab Function, I call a function like this one :

function salary = salary_job(job)

job_char =  char(job) ; % as Simulink not allows to pass strings between blocks, job is "double"

switch job_char

     case 'fireman'

       salary = 1000 ;

     case 'policeman'

       salary = 1200 ;

    case 'teacher'

       salary = 900 ;

etc...

 end

Simulink returns me this error :

"SWITCH expression has indeterminate size."

How to resolve this error without giving the same size to each 'string' ?

Thank you by advance,

Amaury.