Custom Validation for Invoice Lines in Payable Invoice Workbench

Summary:

Hello

We want to do custom validation on the Invoice Lines in the Payables Invoice Workbench. Let's say based on the distribution code combination field entered by the user, we want to validate the the Project#, Asset#, Purchase Order#. The custom validation can be triggered as the user tabs out of these fields or when the Validate action is clicked. We don't want to let the user save the Invoice until all the custom validations have been passed. The validation will be implemented using a Webservice call

Can this be achieved using Page composer or Application Composer without having to create a new custom UI ?