Compare content of columns in two workbooks - output/visual as a dropdown list to show matching %'s

[seville90]

In Spreadsheet 1 I have the following:

Column A - Filename
Column B - Folder name
Column D - Parent folder name

In Spreadsheet 2 I also have the following:

Column A - Filename
Column B - Folder name
Column D - Parent folder name

I need to compare a 'before' (Spreadsheet 1) and an 'after' (Spreadsheet 2).

I need to be able to group by Folder name and Parent folder name and see the matching % when doing so.
e.g. Folder "Folder 1" on Spreadsheet 1 has 1000 files associated to it. However on Spreadsheet 2 it has 900 files associated to it.
Therefore when selecting Folder 1 from a dropdown list of folders, it shows matching as 90%.

I'd also like to be able to select the Parent folder names from a dropdown which calculate/show the total matching % of files across all child folders.

How would I achieve something like this? I'd like a user friendly front page with a dropdown essentially where users can first select the parent folder and secondly (optional) select the child folder to see the matching %'s.

Thanks

Very basic visual of the columns below. But the actual spreadsheets have over 400,000 rows.

Book1
	A	B	C	D
1	Filename	Folder Name	xxx	Parent Folder name
2	File 1	Folder 1		Parent 1
3	File 2	Folder 1		Parent 1
4	File 3	Folder 1		Parent 1
5	File 4	Folder 2		Parent 1
6	File 5	Folder 3		Parent 1
7	File 6	Folder 3		Parent 1
8	File 7	Folder 4		Parent 1
9	File 8	Folder 5		Parent 1
10	File 9	Folder 5		Parent 1
11	File 10	Folder 5		Parent 1
12	File 11	Folder 5		Parent 2
13	File 12	Folder 6		Parent 2
14	File 13	Folder 6		Parent 2
15	File 14	Folder 7		Parent 2
16	File 15	Folder 8		Parent 2
17	File 16	Folder 8		Parent 2
18	File 17	Folder 8		Parent 2
19	File 18	Folder 9		Parent 2
20	File 19	Folder 9		Parent 2
21	File 20	Folder 10		Parent 2
Sheet1