How to add a button in the Account Information Tab?

Question

I am trying to add a button in the Customers->Account Information tab. I want the button to do an action when it is clicked. I would like to do this in a custom module. I'm not too fond of the idea of rewriting core files or any classes. From what I have googled people say you can do this using an Observer, an example is here , if that is true then I would like to do it this way.

I know how to make a basic module, what I need help on is how do you put a button in a specific tab without rewriting the files/classes?

Update 11/3/2013 11am:

Here is the screenshot

I would like to add the button on this tab.

Update 2:48pm 11/3/2014

Here is my code so far, maybe I am making a mistake somewhere.

My file structure

-app
    -local
        -Rdtmodules
            -ChangeGroupNotification
                -etc
                    -config.xml
                -Model
                    -Observer.php
    -etc
        -modules
            -Rdtmodules_ChangeGroupNotification.xml

config.xml

<?xml version="1.0" encoding="UTF-8"?>
    <config>
        <modules>
            <Rdtmodules_ChangeGroupNotification>
                <version>1.0.0</version>
            </Rdtmodules_ChangeGroupNotification>
        </modules>
        <global>
            <models>
                <rdtmodules_changegroupnotification>
                    <class>Rdtmodules_ChangeGroupNotification_Model</class>
                </rdtmodules_changegroupnotification>
            </models>
            <events>
                <adminhtml_block_html_before>
                    <observers>
                        <rdtmodules_changegroupnotification>
                            <class>rdtmodules_changegroupnotification/observer</class>
                            <method>sendCustomerGroupChangeNotification</method>
                            <type>singleton</type>
                        </rdtmodules_changegroupnotification>
                    </observers>
                </adminhtml_block_html_before>
            </events>
        </global>
    </config>

Observer.php

<?php 

class Rdtmodules_ChangeGroupNotification_Model_Observer {
    public function sendCustomerGroupChangeNotification(Varien_Event_Observer $observer) {
        $block = $observer->getEvent()->getData('block');
        if($block->getId() == 'customer_edit' && $block->getRequest()->getControllerName() == 'customer_edit') {
            $block->addButton('test_print', array(
                'label'     => 'Test',
                'onclick'   =>'setLocation(\'' . $block->getUrl('html/sales_order/print') . '\')',
                'class'     => 'go'
        ));
        }
    }
}

Answer 1

So I figured it out. @R.S. helped me get to the right direction but gave me the wrong conditions for my if statement :l. I appreciate the guidance though. Thank you.

So I figured the problem was with my if statements since everything else was working. So first here is my code for the observer.

Observer.php

<?php
class Rdtmodules_GroupNotification_Model_Observer
{
    public function sendNotification(Varien_Event_Observer $observer){
        $block = $observer->getEvent()->getData('block');
        if($block->getNameInLayout() == 'customer_edit' && $block->getRequest()->getControllerName() == 'customer') {
            $block->addButton('test_print', array(
                'label'     => 'Test',
                'onclick'   =>'setLocation(\'' . $block->getUrl('html/sales_order/print') . '\')',
                'class'     => 'go'
            ));
        }
    }       
}

the $block->getId() didn't return anything which is why it wasn't working. Also the controller name was not customer_edit it was just customer o.o.

How i figured this out was I printed the controller names action names and block names in the layout.

echo "Controller Name: " . $block->getRequest()->getControllerName();
echo "Action Name: " . $block->getRequest()->getActionName();
echo "Block Name: " . $block->getNameInLayout();

That is how I figured out what the problem was.

Very useful.

Answer 2

To add a button next to "Back, Reset, ...", try create a custom module with an observer.

in config.xml

<events>
    <adminhtml_block_html_before>
        <observers>
        <MagePal_CustomerButton>
            <class>MagePal_CustomerButton_Model_Observer</class>
            <method>orderPageButton</method>
            <type>model</type>
        </MagePal_CustomerButton>
        </observers>
    </adminhtml_block_html_before>
</events>

In observer.php

class MagePal_CustomerButton_Model_Observer
{
    public function orderPageButton( Varien_Event_Observer $observer )
    {
      $block = $observer->getEvent()->getData( 'block' );

        if($block->getType() == 'adminhtml/customer_edit' && $block->getRequest()->getControllerName() == 'customer')
        { 
            $block->addButton('test_print', array(
                'label'     => 'Test',
                'onclick'   => 'setLocation(\'' . $block->getUrl('html/sales_order/print') . '\')',
                'class'     => 'go'
            ));
        }
    }
}