CRM 2011 HideTab

Hello-

I am working in CRM2011.  I created a custom form with 9 tabs.  2 tabs will be visible always and I want to hide 7 tabs on load.  Of the 7 I only wabt tabs to be visible based on a selected picklist value.  I wrote the below code but it is not working.  It is OnLoad and OnChange event. Error 'tab_1' is undefined.

function hideTabSection() {
    if (Xrm.Page.getAttribute("cpdc_requesttype").getSelectedOption() == null) {
        Xrm.Page.ui.tabs.get("tab_1").setVisible(false);
        Xrm.Page.ui.tabs.get("tab_4").setVisible(false);
        Xrm.Page.ui.tabs.get("tab_6").setVisible(false);
        Xrm.Page.ui.tabs.get("tab_7").setVisible(false);
        Xrm.Page.ui.tabs.get("tab_8").setVisible(false);
        Xrm.Page.ui.tabs.get("tab_9").setVisible(false); 
        Xrm.Page.ui.tabs.get("tab_10").setVisible(false);         

    } else {
        var option = Xrm.Page.getAttribute("cpdc_requesttype").getSelectedOption().text;
        if (option == "Add/Edit Internal Event") {
            Xrm.Page.ui.tabs.get("tab_1").setVisible(true);
            Xrm.Page.ui.tabs.get("tab_4").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_6").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_7").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_8").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_9").setVisible(false); 
            Xrm.Page.ui.tabs.get("tab_10").setVisible(false);  
        } else if (option == "Lawyer Departure") {
            Xrm.Page.ui.tabs.get("tab_4").setVisible(true);
            Xrm.Page.ui.tabs.get("tab_1").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_6").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_7").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_8").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_9").setVisible(false); 
            Xrm.Page.ui.tabs.get("tab_10").setVisible(false); 
        } else if (option == "Total Bio Change") {
            Xrm.Page.ui.tabs.get("tab_6').setVisible(true);
            Xrm.Page.ui.tabs.get("tab_1").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_4").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_7").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_8").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_9").setVisible(false); 
            Xrm.Page.ui.tabs.get("tab_10").setVisible(false);  
        } else if (option == "Bio Section Change") {
            Xrm.Page.ui.tabs.get("tab_7").setVisible(true);
            Xrm.Page.ui.tabs.get("tab_1").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_4").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_6").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_8").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_9").setVisible(false); 
            Xrm.Page.ui.tabs.get("tab_10").setVisible(false); 
        } else if (option == "PG/IG Capability Change") {
            Xrm.Page.ui.tabs.get("tab_8").setVisible(true);
            Xrm.Page.ui.tabs.get("tab_1").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_4").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_6").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_7").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_9").setVisible(false); 
            Xrm.Page.ui.tabs.get("tab_10").setVisible(false);   
        } else if (option == "New Joiner") {
            Xrm.Page.ui.tabs.get("tab_9").setVisible(true);
            Xrm.Page.ui.tabs.get("tab_1").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_4").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_6").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_7").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_8").setVisible(false); 
            Xrm.Page.ui.tabs.get("tab_10").setVisible(false);  
        } else if (option == "PR News") {
            Xrm.Page.ui.tabs.get("tab_10").setVisible(true);
            Xrm.Page.ui.tabs.get("tab_1").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_4").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_6").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_7").setVisible(false);
            Xrm.Page.ui.tabs.get("tab_8").setVisible(false); 
            Xrm.Page.ui.tabs.get("tab_9").setVisible(false);  
        }
    }
}