Module development and code questions

Hi all, I'm trying to create a module that will do the following task (for 4.7)

(1) when a node is created/edited, create a radio button on the editting/adding page.
(2) if the radio button is selected, extract the body's text and process it in some way

Which hooks do I need to look at? Any pointer?

Thanks alot.
vph

Thought I'd checkin to see if anyone has a "convention / conference" scheduling module in the works? What I am looking for is something that will hande:

I have been noodling over this off & on for a couple days, cruising the forums, not finding an answer:

I have a custom node that has a multi-select box. Like this:

Can anyone point me in the direction of any resources concerning using a custom search page and displaying it in a tablesort with a pager in 4.7?

The requirements of the project are to create a search form that consists of:

http://drupaldocs.org/api/head/function/hook_menu says: Every set of local tasks should provide one "default" task, that links to the same path as its parent when clicked.

Why?

I have a list of services displayed on a page, and when one service is clicked the user gets presented with a set of tabs under which they may modify different items. I do want one 'default' task which will be the tab which is selected by default (ie the first tab). I do not, however, want it to link to the parent, which is the service list - that makes no sense to my interface, where the service list is a link in the Navigation Block already.

I have tried to make all three tab items 'type' values into MENU_LOCAL_TASK but then the first one behaves the same as a MENU_DEFAULT_LOCAL_TASK: It links back to the service list instead of linking to the 'url' I entered in the array in hook_menu. So the user cannot return to the first tab once he has visited the second tab; he needs to select the service again from the list.

How can I disable this 'default' tab behaviour, or work around it to force all three of my tabs to point to their 'url's as defined in the hook_menu function?

$links[] = array('path' => 'services/'.$q[1].'/edit/basic',
'title' => t('Basic'),
'callback' => 'edit_basic',
//'access' => TRUE,

I'm relatively new to Drupal but I'm digging in deeply and making my own custom node type. It has a seperate mysql table to store data (flexinode didn't do as much as I needed). So far I've got the basics working pretty well, but I dont see any docs on what hook Drupal calls when creating a new revision. I thought it would be hook_update, but I don't see that running. I want to create a new corresponding version of my data whenever a new revision of the node is created.

Thanks!