If your provider granted you permission to manage domains through Plesk XML interface, you may want to take advantage of automated creation of domains in Plesk as your customers purchase domain names and hosting plans through your web site. To implement such mechanisms, you should possess a strong knowledge of programming languages, and be experienced in web application development.
To learn more about using Plesk XML interface (also referred to as Plesk API RPC), please visit http://download1.sw-soft.com/Plesk/Plesk7.5/Doc/plesk-7.5r-sdk-html/docs/plesk_agent/ch01.html
Plesk client accounts can be authorized to perform only the following operations through Plesk API RPC: creating and removing domains in Plesk, modifying miscellaneous domain preferences and hosting services, retrieving information on domains.