function soloNumerosEnteros(caja){
   if (caja.value == ","){
		caja.value=caja.value.slice(0,length-1)
		caja.focus();
		return false
	}
   if (caja.value != ""){
		for (var i=0; i<caja.value.length; i++){
			var caracter = caja.value.substring (i, i+1);
			if(caracter < "0" || caracter > "9"){
				caja.value=caja.value.slice(0,length-1)
				caja.focus();
				return false
			}
		}
	}
}