en un abrir y cerrar de ojos

Etymology
lit. 'in an opening and closing of eyes'.

Adverb

 * 1)  in the wink of an eye, in the blink of an eye, in the twinkling of an eye
 * 2)  at the drop of a hat, at a moment's notice, in a heartbeat
 * 1)  at the drop of a hat, at a moment's notice, in a heartbeat