function isPageNumberValid( pageNumber, minPageNumber, maxPageNumber ) {
  
  if ( isNaN(pageNumber) ) {
    alert("LANG_CATALOG_JS_MUST_PROVIDE_A_NUMBER_FOR_PAGE");
    return false;
  } 
  
  if ( pageNumber > maxPageNumber ) {
    alert("LANG_CATALOG_JS_PAGE_NUMBER_HIGHER_THAN_MAX_PAGE");
    return false;
  }
  
  if ( pageNumber < minPageNumber ) {
    alert("LANG_CATALOG_JS_PAGE_NUMBER_LOWER_THAN_MIN_PAGE");
    return false;
  }

  return true;
}