Automatic copying of text in Header text of PO

Dear Friends,

We have got following requirement.

Currently our client,while creating Purchase Order,he is entering already stored text connected to that Purchase Order in the Header text against Purchase order text.He is pasting the text here whenever this type of purchase order is created.

Is there any facility in SAP,whenever the concern document type is created or selected,automatically connected text will be copied in the header text of PO.

Please suggest.

Regards,

Dayanand