Excel中的分层动态下拉列表

Question

In my firm, I've a database like this and I want to create a hierarchical dynamically updating drop down list.

+-----------+----------+--------+
| Institute | Industry | Course |
+-----------+----------+--------+
| a         | aa       | aaa    |
| a         | aa       | bbb    |
| b         | bb       | mmm    |
| b         | cc       | ddd    |
| b         | bb       | ttt    |
| c         | ee       | fff    |
| d         | ee       | ggg    |
+-----------+----------+--------+

I want the end result to be something like this. The user will start from the top. Depending on top entry bottom list will change accordingly. Below is a snapshot.

My User Entry List Demo Structure

My Approach

My plan was to create an array formula which indexes the course list based on the first two entry. Then use offset to take the course entries. But my problem is though I am able to index the course list I am not able to sort them to use in data validation. And data validation does not ignore the non-filled or error values, which I don't want. Assuming I solved the first hierarchy problem and I've the Institute and Industry output. I tried this

G8 - Institute Input from drop down
G9 - Industry Input from drop down
H11:H15 - respective courses

And the formula in H11:H15 is {=INDEX(C2:C8,1/(1/((A2:A8=G8)*(B2:B8=H8)*(ROW(C2:C8)-1))))}
Here is the output I'm getting.

I am fairly new to posting questions. Let me know if I can make it more clear. Also, I found these very useful links while surfing the internet. Pardon me for adding as code, as SO doesn't allow more than 2 links for new members

1: http://www.contextures.com/xlDataVal02.html
2: https://www.ablebits.com/office-addins-blog/2014/09/30/dependent-cascading-dropdown-lists-excel/

Answer 1

I think what you want is to put this formula as an array into H11:H18:

=IFERROR(INDEX(C2:C8,AGGREGATE(15,6,(ROW(C2:C8)-1)/((A2:A8=G8)*(B2:B8=G9)),ROW()-ROW(H10)),1),"")

Then you can set your data validation for the course option to H11:H18.