Hello all. I have some jquery on my form that shows/hides divs based on the chosen value of a drop down menu

Code:
function show1() {
   var div_num = $("#airpvtyesno").val();
   if (div_num == 0) {
   $("#pickuppvt").hide(); 
   $("#pickuplhr").hide(); 
	};
   if (div_num == 1) {
   $("#pickuppvt").hide(); 
   $("#pickuplhr").show(); 
   	};
	   if (div_num == 2) {
   $("#pickuppvt").show(); 
   $("#pickuplhr").hide();
	};
}
I am trying to implement a rule on my form that if a specific form element is left empty, the form cannot be processed and an alert is called.

Here is an example of the javascript I use for that feature:

Code:
function IncompleteForm()
{
var FormOk  = true;

	if (document.myform.myfield.value == '')
    {
        alert('Please enter a value for this field.');
        document.myform.myfield.focus();
        FormOk = false;
	};

return FormOk;

}
However, I need to combine the two features.

I only want specific field elements to run this rule if the div they are contained in is shown.

It would ideally look something like this:

Code:
function show1() {
   var div_num = $("#airpvtyesno").val();
   if (div_num == 0) {
   $("#pickuppvt").hide(); 
   $("#pickuplhr").hide(); 
	};
   if (div_num == 1) {
   $("#pickuppvt").hide(); 
   $("#pickuplhr").show(); 
   IF pickuplhr.FIELD1 IS EMPTY - ALERT - PLEASE ENTER A VALUE FOR FIELD 1
   	};
	   if (div_num == 2) {
   $("#pickuppvt").show(); 
   $("#pickuplhr").hide();
   IF pickuppvt.FIELD2 IS EMPTY - ALERT - PLEASE ENTER A VALUE FOR FIELD 2

	};
}
my limited ability in jquery and general syntax is giving me difficulties combining these features.

as always any help is much appreciated. thanks