My opinion ,
If he want vesper as constant enchant then @Evie Frye showed the code ,
else if he want to maintain dynasty enchant he go with npc_%objectId%_exc_multisell XXXX .
with multisell including this :
<item id="1">
<ingredient id="7140" count="2500"/>
<ingredient id="10001" count="1"/>
<production id="10300" count="1"/>
</item>