Renaming

[C# Programming]

I have this little code who is adding that number to a listbox1, already make in the UI.
What I want is to RENAME the listbox1 to lb, BUT inside this void ONLY.(I think of it as a some sort of variable when I want to rename it.)
HOW TO DO IT?

public void ListBoxItemAdd()
{
listBox1.Items.Add("12345");
}

Thanks
~Teodor~