Payaments : Custom Validation

We have a requirement to perform some custom validation after Build Payment program completes.

The reason we can't include this as a custom validation either at document/payment/instruction level is because we need the check number/payment reference number which is generated only if payment instruction is created successfully.

I was planning to trigger this custom process using fnd.conc.request.completed business event after Build Payment program completes.

Now what I understood is once Build Payments completes it triggers Format Payment Instructions.

Let's say if Format Payment Instructions completes and the status of Instruction and Payment Process Request is changed to 'FORMATTED'. Is there a way to keep either the Payment Process Request or Payment Reference OnHold/Pending Review? programatically in my custom code until the validation completes and then release the hold.