The reason behind asking for an actual file enables us to work within your actual case.
Excel is very broad and there are numerous methods to achieve the same end.
it is counter productive to suggest a method that conflicts with the rest of your code.
My personal preference is to work with tables and arrays to populate combos/listboxes.
Rowsource is a method I rarely use due to its instability when used with large amounts of data transference.
A simple example file is attached, you will see in the code the transfer of each element of the listbox choice to individual textboxes.