CustomModelAdmin.php

<?php

class CustomModelAdmin extends ModelAdmin {

  public function SettingsForm()
  {
    if ($this->request->isPOST()) {
      $form = $this->getSubsectionForm(); //returns from CMSForm::create($this, 'SettingsForm', ...)
      $form->loadDataFrom($this->request->postVars());
      foreach ($this->request->postVars() as $name => $val) {
        if (strpos($name, 'action_') === 0) {
          $actionName = substr($name, strlen('action_'));
          if ($this->hasMethod($actionName)) {
            $this->{$actionName}($form->getData(), $form);
          }
        }
      }
      return $form->forTemplate();
    } else {
      return $this->getSubsectionForm();
    }
  }
}