Asking for confirmartion on node creation I want ask for confirmation if a duplicate node is getting created. But how do I do it?

I know how to do it if I'm creating the form myself but in node creation I'm not creating the form.

I also know Drupal confirm_form, how "storage" is used in multistep forms. But how to use it along with the code which is not mine. Where to plug it?
@AgA: "I want ask for confirmation if a duplicate node is getting created. But how do I do it?"

The way you do it is to validate any new node added by a user against existing nodes.

Towards this end, hook_node_validate() is your friend. :-) You'd make a module that implements hook_node_validate(), and within that function do a query using the data the user input. If you find similar nodes that already exist, you can form_set_error() an error message. Click through to the API site and there's even some sample code.