Dear Yasin
Your query isn't clear at all. It seems like you want to create a Dummy Asset at the time of PO and a real asset at the time of MIRO? What is the basic object of doing that?
What i have understood from above is that you do want to create a PO, but dont want to consume any budget on it in case of an Asset. While you want to consume it at the time of MIRO.
Can you elaborate it further in details.
Regards,
Amar