Error with field's customized event Field: window Event:onload

function Form_OnLoad()
{
    setDepartmentDisabled();
    setFormState();
}

function setDepartmentDisabled()
{
    var department = Xrm.Page.ui.controls.get('aai_department');
    if (department != null && department != 'undefined')
    {
        var formType = Xrm.Page.ui.getFormType();

        switch (formType)
        {
            case FORM_TYPE_CREATE:
                department.setDisabled(false);
                break;

            default:
                var value = getSelectedOptionValue(department.getAttribute().getName());
                switch (value)
                {
                    case 100000000:
                    case 100000001:
                    case 100000002:
                    case 100000003:
                        department.setDisabled(true);
                        break;

                    default:
                        break;
                }
                break;
        }
    }
}

function setFormState()
{
    var value = getSelectedOptionValue('aai_department');
    switch (value)
    {
        case 100000000: //Underwriting
        case 100000001: //Asset Management
            setVisible(TAB_ZONING, false, requiredFieldsZoning);
            setVisible(TAB_UNDERWRITING_AND_ASSETMANAGEMENT, true, requiredFieldsUnderwritingAssetManagement);
            //setVisible(SECTION_CLOSING, false, requiredFieldsClosing);
            Xrm.Page.getAttribute("new_oversight").setRequiredLevel("required");
            Xrm.Page.getAttribute("new_underwriter").setRequiredLevel("none");
            Xrm.Page.getAttribute("new_analyst").setRequiredLevel("required");
            Xrm.Page.getAttribute("aai_kickoff").setRequiredLevel("none");
            Xrm.Page.getAttribute("aai_duedate").setRequiredLevel("none");
            Xrm.Page.getAttribute("aai_deliverydate").setRequiredLevel("none");
            break;

        case 100000002: //Zoning
            setVisible(TAB_ZONING, true, requiredFieldsZoning);
            setVisible(TAB_UNDERWRITING_AND_ASSETMANAGEMENT, false, requiredFieldsUnderwritingAssetManagement);
            //setVisible(SECTION_CLOSING, false, requiredFieldsClosing);
            Xrm.Page.getAttribute("new_oversight").setRequiredLevel("none");
            Xrm.Page.getAttribute("new_underwriter").setRequiredLevel("none");
            Xrm.Page.getAttribute("new_analyst").setRequiredLevel("required");
            Xrm.Page.getAttribute("aai_kickoff").setRequiredLevel("required");
            Xrm.Page.getAttribute("aai_duedate").setRequiredLevel("required");
            Xrm.Page.getAttribute("aai_deliverydate").setRequiredLevel("none");
            break;

        case 100000003: //Closing
            setVisible(TAB_ZONING, false, requiredFieldsZoning);
            setVisible(TAB_UNDERWRITING_AND_ASSETMANAGEMENT, true, requiredFieldsUnderwritingAssetManagement);
            //setVisible(SECTION_CLOSING, false, requiredFieldsClosing);
            Xrm.Page.getAttribute("new_oversight").setRequiredLevel("required");
            Xrm.Page.getAttribute("new_underwriter").setRequiredLevel("required");
            Xrm.Page.getAttribute("new_analyst").setRequiredLevel("none");
            Xrm.Page.getAttribute("aai_kickoff").setRequiredLevel("required");
            Xrm.Page.getAttribute("aai_duedate").setRequiredLevel("required");
            Xrm.Page.getAttribute("aai_deliverydate").setRequiredLevel("none");
            break;


        default:
            setVisible(TAB_ZONING, false, requiredFieldsZoning);
            setVisible(TAB_UNDERWRITING_AND_ASSETMANAGEMENT, false, requiredFieldsUnderwritingAssetManagement);
            //setVisible(SECTION_CLOSING, false, requiredFieldsClosing);
            break;
    }
}

function setVisible(id, value, requiredFields)
{
    if (id != '')
    {
        var tab = Xrm.Page.ui.tabs.get(id);
        tab.setVisible(value);
}