How to make Child Items read-only base on a field value of the Parent Record?

[Triggerz]

Hi,

How can I restrict the editing and adding of Child Items base on a field value of the Parent Record?
The reason is that if the Parent Record status field value is updated to "Posted", I don't want any user to be able to modify or add child items anymore.

Thanks in advance...

[a.slyzhko]

Create API before save script for you child entity type.

if (parentId && parentType) {
    $parentStatus = record\attribute(parentType, parentId, 'status');
    if ($parentStatus == 'Posted') {
        recordService\throwForbidden('Parent status is set to Posted. Adding new items and modifying existing is forbidden.')
    }
}