Rules for Submitting a Sales Order

Hi, I would like to make a rule where a specific document cannot be submitted without certain criteria being met.
In this case, we have created a field with 3 order types, and I would like the rule to come into effect so that someone can only submit a sales order if it is a specific order type.
I haven’t been able to locate any information on how to do this.

You may be looking for Workflows in ERPNext. Check if this works for you -

https://docs.erpnext.com/docs/v13/user/manual/en/setting-up/workflows

maybe python script is more easy and straight forward.