FTP Access with Host Headers???

We have Windows NT 4.0 with IIS 4.0 and we want to set up multiple public web sites using one IP address (host headers), but we are unsure how to handle the problem of FTP access to the various site directories.

We want the users to be able to FTP in to manage their respective site content, but we’re not sure if this is possible using the DNS name only. Does anyone know if this is possible or if there is a third party solution for this?