Multiple mandatory fields

Multiple mandatory fields

Hello, I'm trying to ensure that several fields are filled in based on following statement. 
if(DeliveryOption == "משלוח")
Each field should produce different error message

So I've created several "rules", one for each mandatory field like this:

if(DeliveryOption == "משלוח" && DeliveryCity == null)
{
alert "יש להזין עיר למשלוח";
cancel submit;
}

if (( DeliveryOption == "משלוח" ) && (RecipientStreet == null))
{
alert "יש להזין רחוב למשלוח";
cancel submit;
}

if (( DeliveryOption == "משלוח" ) && (RecipientHouseNum == null))
{
alert "יש להזין מספר בית למשלוח";
cancel submit;
}

if (( DeliveryOption == "משלוח" ) && (RecipientAprtmntNum == null))
{
alert "יש להזין מספר דירה למשלוח";
cancel submit;
}

if (( DeliveryOption == "משלוח" ) && (RecipientFloor == null))
{
alert "יש להזין קומה למשלוח";
cancel submit;
}

When I paste it as is, only the first field  DeliveryCity works.
So either I should create several scripts (one for each field) or try to integrate all those rules in one.

Can anybody point me out to the right direction?

Thanks,
Igal