How can I prevent a form from being saved when the values coming from another table are empty?

[maretec]

I have an app for loans. These loans are related to vehicles.

I have a table from where I create a document with a bot (Document table), using values of the vehicles table. The document is created with no problem when all values coming from the Vehicles table exist, but if there's any empty value, there is problem with the bot.

I can't set all fields as required in the Vehicles table.

How can I prevent the form of the Document table from being saved when some values coming from the Vehicles table are empty?