Another JS Loop Question

I have this script, and I need to implement an if statement into it. How shall I go about doing this?

    class CityWizard extends ScriptableWizard {

var ground : GameObject;
var numberOfBuildings : int = 20;
var inititalBuildingNumber : int =20;
var numberOfRows : int = 5;
var building1 : GameObject;
var building2 : GameObject;
var building3 : GameObject;
var MyPosition = Vector3(10, 0, 10);
var buildingType = 4;
var zchange = 10;
var nothing : GameObject;
var rowchange = 0;
var rowchangeIncrease = 10;
var i : int = 20;

@MenuItem("GameObject/City!")

static function City (){
ScriptableWizard.DisplayWizard("Title", CityWizard, "City", "");
}

function OnWizardCreate() { 

        inititalBuildingNumber = numberOfBuildings;
        var newObj = Instantiate (ground, Vector3(0,-0.1,0), Quaternion.identity);
        newObj.transform.localScale.z = numberOfBuildings*40;
        newObj.transform.localScale.x = numberOfRows*100;   

        for(i=0; i <=20; i++){
            if (i==0){        
            if (numberOfRows > 0){
            print ("next");
        MyPosition += Vector3 (rowchangeIncrease,0,-(zchange*inititalBuildingNumber));
        i += 20;
        rowchange += rowchangeIncrease;
        numberOfRows--;
        }
        }
        print (buildingType);

        buildingType = Mathf.Floor(Random.Range(1,5));

    switch (buildingType) { 

    case (1) :   
        Instantiate (building1, MyPosition, Quaternion.identity);
        MyPosition += Vector3 (0,0,zchange);

    break;

    case (2) : 
        Instantiate (building2, MyPosition, Quaternion.identity);
        MyPosition += Vector3 (0,0,zchange + 3); 

    break; 

    case (3) : 
        Instantiate (building3, MyPosition, Quaternion.identity);
        MyPosition += Vector3 (0,0,zchange+3);

    break;

    case (4) : 
        Instantiate (nothing, MyPosition, Quaternion.identity);
        MyPosition += Vector3 (0,0,zchange);

    break;

        }
        }

    }

function OnWizardUpdate (){
    helpString = ("Select City Parameters!");

}
}

Place it inside the for loop but before or after the switch statement? ... I don't know when do you want it to be executed? o.O