Código:
  
Espero puedan ayudarme a solventar este problema, gracias. function validar();
{
if(!document.form1.nuevobarco.checked && madeSelectionIMO(IMO,"Please select a ship IMO")){				
if(document.form1.nuevobarco.checked && notEmpty(imonuevo, "Please enter the new Ship IMO")) {
return true;
}
}
return false;
}
function madeSelectionIMO(elem, helperMsg){
	if(elem.value == "Select IMO..."){
		alert(helperMsg);
		elem.focus();
		return false;
	}else{
		return true;
	}
}
function notEmpty(elem, helperMsg){
	if(elem.value.length == 0){
		alert(helperMsg);
		elem.focus(); // set the focus to this input
		return false;
	}
	return true;
}
 

