Script code adjustment request

I would like some help with adjusting this script in our custom calculation field:

// Get the field values, as numbers

var Goals = +getField("Goals").value;

var GA1 = +getField("GA1").value;

var GB1 = +getField("GB1").value;

var GC1 = +getField("GC1").value;

var GD1 = +getField("GD1").value;

// Set this field value

switch (Goals) {

case 1:

    event.value = GA1;

    break;

case 2:

    event.value = (GA1 + GB1) / 2;

    break;

case 3:

    event.value = (GA1 + GB1 + GC1) / 3;

    break;

case 4:

    event.value = (GA1 + GB1 + GC1 + GD1) / 4;

    break;

default:

    event.value = "";

    break;

}

It was written when our form's "Goals" had the numbers 1 through 4 as options.  Now we have 0 through 4 as options - so shouldn't there be a "case 0" added to this? 

Thank you for any help you can give.