How to link Purchase module details with CMDB module thru machine serial/tag numbers?

How to link Purchase module details with CMDB module thru machine serial/tag numbers?

Dears,
 
I would like to link my purchase module details with CMDB module which is very helpful to us and less time consuming to update.  I am hoping to do the same thru machine serial/tag numbers which is automatically detected by the CMDB, I just don't know where to include the same in my Purchase module so that CMDB module will capture the details and publish the information automatically.
 
Many thanks,
Dawood E.A.