How to create a rule that rejects a purchase order when it has no source agreement

Summary:

We need to somehow get the purchasing document approval flow to reject POs that don´t have a source agreement.

Content (please ensure you mask any confidential information):

We are trying to create a purchase approval rule where purchase orders that do not come from a purchase request or an agreement (either one or the other) are rejected.

We have tried to add a condition to the rule with the attribute "agreement amount is blank" but it does not work and does not refer to this rule in case of no agreement or purchase requisition.

Version (include the version you are using, if applicable):