defined('_JEXEC') or die;

global $_CB_framework, $_PLUGINS, $mainframe;

if ( defined( 'JPATH_ADMINISTRATOR' ) )
{
	if ( ! file_exists( JPATH_ADMINISTRATOR . '/components/com_comprofiler/plugin.foundation.php' ) ) {
		echo 'CB not installed!';
		return;
	}
 	include_once( JPATH_ADMINISTRATOR . '/components/com_comprofiler/plugin.foundation.php' );
}
else
{
	if ( ! file_exists( $mainframe->getCfg( 'absolute_path' ) . '/administrator/components/com_comprofiler/plugin.foundation.php' ) )
	{
		echo 'CB not installed!';
		return;
	}
	include_once( $mainframe->getCfg( 'absolute_path' ) . '/administrator/components/com_comprofiler/plugin.foundation.php' );
}

cbimport( 'cb.html' );

class plgMyPlugin extends JPlugin
{
...
  public function onUserAfterLogin($options)
  {
      ....
      $theField=$this->myFunction();
  }
  public function myFunction
  {
	    global $_CB_framework;
 
		$myId = $_CB_framework->myId();
		$cbUser =& CBuser::getInstance( $myId );

		if ( ! $cbUser ) 
		{
			$cbUser =& CBuser::getInstance( null );
		}
 
		//$user =& $cbUser->getUserData();
		
		$theField = $cbUser->getField(....);
  }
}