See the Help page for `beforeLoad`:

>>

Notes: beforeLoad user events cannot be triggered when you load/access an online form. Data cannot be manipulated for records that are loaded in beforeLoad scripts. If you attempt to update a record loaded in beforeLoad, the logic is ignored. Data can be manipulated for records created in beforeLoad user events. Attaching a child custom record to its parent or detaching a child custom record from its parent triggers an edit event.