Adding a php script to registration sequence

Greetings,

I have written a php script designed to take a block of html code, do a str_replace to insert the newly registered user's name, then update the appropriate field in the comprofiler table. This should happen only once per user, at the end of the registration sequence.
My question is where do I attach the script? Should it be in the "URL for first login visit" field in the registration setting page? If so, what would be the specifics?

Any help would be appreciated.

Thanks,
Gizmogle

joomla 1.5.22
CB 1.3.1

I think you can use incubator project CB Code available to Professional Members
www.joomlapolis.com/cb-solutions/incubator

bye