Select_one choice filter from another select_one

Hi,
I want to create a selection list (select_one) which should be filtered regarding the option selected in another selection list (select_one).
The first select_one contains the 7 characters of the second select_one. What I want is that for the second select_one only display those options matching the 7 characters of the first select_one.
The file can be downloaded using the following link: “removed link”