Default latest created PO Number in the screen

Hi,

I have one Z program developed for PO print.

It is very much similar to standard ME9F transaction / program.

In ME9F transaction, as soon as we execute a transaction. The latest created PO number will appear onthe PO document filed.

The same is expected to do in Z developed print transaction.

Becaz it won't display newly / latest created document number.

Any one helps me how to make a field with the default value of newly created PO document number.

Your help is appreciated and Awarded suitably for helpful answers.

Thanks in advance.

Giri