Changes

1- Create a custom field "soccpy_nom" constrained on llx_society that will duplicate the society's id. This is necessary because other custom fields can only be cascaded using other custom fields, not any Dolibarr fields. Using duplication allows you to duplicate any Dolibarr field (and even $_GET and $_POST), so that you can use them to cascade. Copy the parameters as shown in this image:

1- Create a custom field "soccpy_nom" constrained on llx_society that will duplicate the society's id. This is necessary because other custom fields can only be cascaded using other custom fields, not any Dolibarr fields. Using duplication allows you to duplicate any Dolibarr field (and even $_GET and $_POST), so that you can use them to cascade. Copy the parameters as shown in this image:

2- Create a custom field "contact_firstname_lastname" with Cascade option with parent "soccpy_nom" and constrained on the table llx_socpeople (the table of the contacts), which will show the list of contacts associated only to the selected society in soccpy_nom. Copy the parameters as shown in this image:

2- Create a custom field "contact_firstname_lastname" with Cascade option with parent "soccpy_nom" and constrained on the table llx_socpeople (the table of the contacts), which will show the list of contacts associated only to the selected society in soccpy_nom. Copy the parameters as shown in this image:

And voila, you're done! The field soccpy_nom should be hidden so you won't see it, but you should see the field contact_firstname_lastname and you can check that only the contacts related to the society selected for the current invoice are shown.

And voila, you're done! The field soccpy_nom should be hidden so you won't see it, but you should see the field contact_firstname_lastname and you can check that only the contacts related to the society selected for the current invoice are shown.