Hello Emerson,
First of all thank you for your kind support. I cleaned up the module and now it is starting to work. I have still a couple of problems anyway:
1) The dropdown to select the parent attraction now only lists the attraction in the given region, which is perfect. The only point is that it defaults to the first list item. I would like to have the form (that is the form to add a new guided tour) without a chance to insert an unwanted choice. How can I appent to my dropdown an initial 'Select and attraction from the list' with no value?
2) The guided tour also have a parent Guide, which should be the guide currently logged who's currently filling out the form. How can I add a text field containing the guide (single value, not all the listed guides' as a read only field?
Thanks again for your help. I'm sending you a private email with some data.