how to make multiple ajax callbacks from a drop-down field?
In your ajax_command_replace where the form is rendered, do this: ajax_command_replace("#checkboxField", render($form['checkboxField']['values']=$text)), where $text is the value from the checkboxes, as shown below:



function ajax_checkbox_callback($form, &$form_state) {
    return array(
    '#type' => 'ajax',
    '#commands' => array(
    ajax_command_replace("#checkboxField", render($form['checkboxField']['values'] = $value_text_form_text_field_1)),
    ajax_command_replace("#txtField", render($form['txtField']['values'] = $value_text_form_text_field_2))
    )
  ); 
}