Replace composer but only on replys to a topic in one category

[dburmeister]

Hello thanks for any help what I am looking to do is create a plugin that for a category could replace the composer with a "form". what I want is for users to only be able to post a small bit of text say around 100 chars. and then a link to a blog post. Any help in pointing in at what hooks I need would be amazing

Thank you
Dale