Hi,
you can do something like this:

1. Create Field
- Create a select field called "Blocked" (alias blocked) with 2 options:
0|JNO
1|JYES
- Set this select to not show on profile,edit profile and registration pages. With this configuration the field will be available only on backend admin
- Go into Easy Profile Options (Administration->Components->Easy Profile->Options button)
- Enable parameter called "Admins can show not editable fields in frontend", this parameter allow you to see not editable fields also in frontend when admins try to change others profiles (Available only on latest release 1.4.3)

2. Make plugin to block user
To block user you need to develop a simple plugin that make this, follow these steps:
- Download, Install and Enable Skeleton Plugin (you will find it at http://docs.easy-profile.com/index.php/article/triggers)
- Open file /plugins/jsn/skeleton/skeleton.php
- remove samples functions: triggerFieldAvatarUpdate, triggerProfileUpdate
- add function like this:

public function triggerProfileUpdate($user, &$data, $changed, $isNew)

	{

                if( isset( $data['blocked'] ) && $data['blocked'] == 1 ) {

                    $db = JFactory::getDbo();

                    $query = 'UPDATE #__users SET block=1 WHERE id = ' . $user->id;

                    $db->setQuery($query)->execute();

                }

	}

docs about our triggers at http://docs.easy-profile.com/index.php/article/triggers

NOTE: This code is not tested and not supported, this is only for example purpose. You need to have a minimum of PHP and Joomla Dev knowledges