Making a field mandatory dynamically via OAF in AR Customer Tax Profile page

Hello OAF gurus:

   I'm trying to make Default Registration Number field mandatory in AR Customer Tax Profile page based on certain condition like if the customer address is in EU and if the user org_id is UK, then it should be made mandatory.

   I extended the VO and created a transient variable to type Boolean, imported the jpx file and through SPEL, I tried setting the Required property in OAF Personalization on that field. But, it's not working.

  The same SPEL code works for Read Only and Rendered property. My guess is that since, Read Only and Rendered property takes True or False value, this is working extension is working.