Hi Amit;
What your are talking about is the ability for PB to build an OLE Server COM object. Yes, that feature was removed by Sybase in the PB 12.x days I am sad to say and I have no idea why. 
One suggestion I have for now is stay on PB 11.5. The PB product is being turned over from SAP to Appeon Corporation in the near future. I would suggest contacting them and adding this feature requirement or maybe something equivalent as an enhancement feature request.
Another alternative (instead of .Net that David suggested) is to look at placing your OLE Server code into a Web Service and let your client applications interact with your PB code via WS Calls.
HTH
Regards ... Chris
PS: I feel your pain (PIA).