Programmatically editing a post

[dharris]

How would i go about programatically adding a preset message to the end of a post?

Will be used in a custom ban system, which will add "User was banned for this post by MOD_USERNAME for LENGTH_OF_BAN. Reason given: REASON" to the end of a certain post. I have the postID sorted out, i can probably figure out most of it myself, but it would save a lot of time if you'd tell me how i can take the information (the message, the post id etc) and edit the correct post in the correct way. I just want to add the message to the end, not overwrite it.

Thanks in advance.