follow('fieldname'). This will take the value of the field and assuming the field is a link to another table will follow it, load the other record and update the current record variables to those of the new records. Follow will return true if the operation was successful and false if it wasn't. So if it was not able to follow the link or you misspelled the fieldname it will be false. For that it's recommended that it's used like this: follow('cust_no') and country_code='SWE'. This will try to follow a link to the cust_entity record and from that record see if the cust_entity country_code field is SWE. If there is a problem following the link to the entity the full expression will fail.