Excel VBA TreeView 6.0 - How to add a second level node

Question

Im currently sitting on this issue that I cant create another subitem. My code looks like this:

Private Sub UserForm_Initialize()
With TreeView1.Nodes

    .Add , , "S", "Item1"
    .Add "S", tvwChild, , "SubItem1"
    .Add "SubItem1", tvwChild, , "Sub-SubItem1"
    
 End With       
 End Sub

This line isn't working: .Add "SubItem1", tvwChild, , "Sub-SubItem1". I'll always get an error. Without this line it looks like this so far:

There is another problem, which occured. If I open this Userform, I am able to edit the nodes, how can I prevent this?

Another Question: Isn't there any possibility to do this with a combobox instead of treeview?