entry_id value needed

I want to get the value of the entry id and have placed the following code into my functions.php:

// adds id when you submit form
add_action("gform_pre_submission", "populate_id");
function populate_id( $form ) {
$_POST['input_131'] = RGFormsModel::get_lead($entry_id);
}

where "131" is my field number for the placement.

The reason i need to re populate the ID is b/c client doesnt want the tile of the form at the top. just the id. i can hide the entire "details" column, but now i need to re populate.

thanks!