develop Autonumber configuration

Hello.

as we need autonumber in our CRM, we decide to develop an entity that contains configuration for autonumber. we write some c# code for create step on autonumber entity. when user create a configuration (new record of autonumber entity), the code raise and run. my question is how can i handel this senario described below:

we have 2 fiels on autonumber entity: fieldname and entityname. entityname hold the name of entity that user want to describe autonumber for that. and the fieldname is the name of field on that entity have to hold autonumber that created. how can i handel in my code that when a record of entityname is created, the code raise.

kind regards