Dynamic Changing UserForm Combobox List

Hi,

I am trying to create a user form with two different combo boxes. The first combo box's range is a list of levels in a building and the second I want to be the rooms within the level selected in the first combo box. how can I make it so that excel detects what level is entered in the first combo box and changes the RowSource accordingly for the second combo box to change to a the range of rooms within the level selected. Both these combo boxes are on the same page within a userform.

Thank you very much in advance!

The attached is a method of filtering cascading comboboxes.
Select the pieces of code you require (you will not need all as it demos' selections)
torachan.