Here is the calc. The table from which the script is being called is 'clients', the table which is used for the layouts being selected is called 'Policies'. The field which describes the policy type is 'Policies::Pol_Type' which is a numeric field and its contents are 0,1 or 2 (only testing with 0 and 1 at the moment). The Layouts are named as per the names in the calc field - same case and spaces etc.
Case ( Policies::Pol_type=0; "Assurance Policies"; Policies::Pol_type=1; "Pension Policies" )