Getting Parent Record ID during OnCreate (PreValidate)

Dynamics CRM 2015 On-Premise

Need to do some validations / calculations before a child record is created. Was thinking of a plugin during Create Message (Pre Validate). How can I get the parent ID of the child record being created. We will be using Quick Create form to create the child record (on click on + form the subgrid). Is plugin the right was or should we go for JScript?

Appreciate your help.

Regards

AbD