function hacerMagia(){  

	if (document.miform.combo1.selectedIndex < 0  ||
		document.miform.combo1.selectedIndex < 0 ) {
		alert ('selecciona algo pascual!!');
		return;
	} 

	var valorCombo1 = document.miform.combo1.options[document.miform.combo1.selectedIndex].value;
	var valorCombo2 = document.miform.combo2.options[document.miform.combo2.selectedIndex].value;
	var url = '../' + valorCombo1 + '/' + valorCombo2 + ".php";
	location.href = url;
}