Set the selected item of a listbox or radiolist

[Do]

Is this the correct syntax? I'm missing something about the list items, but
I
don't know where to find it.

CType(e.Item.FindControl("lstEUsertype"), ListBox).SelectedValue() = "E"

I want to automatically select the item in the list that has a corresponding
value of "E". on the Edit command of the datagrid.

But I get this

Object reference not set to an instance of an object.