Create Flat BOM from indented BOM using macro/vba code

Hi,
I am trying to create a flat Bill of Materials (BOM) from an indented bill of materials.
The flat BOM of material should contain the list of all purchased parts required within the indented BOM.
My difficulty is trying to exclude lines on the indented BOM that belong to a purchased item.
I have attached a sample spreadsheet which contains an indented BOM and i have identified the lines i want to include in column A with explanation in column M.
When going through the BOM, if the item is MAKE, then the components of the make item should be included if they are purchased.
Basically my problem is trying to ignore the BOMs associated with purchased parts from the list.

In the sample spreadsheet, the item on line 9 (12620200) is purchased, however it has a BOM. I do not want to include the any of the parts within the BOM of 12620200 in my flat BOM.
in this example - i do not want to identify any part in lines 10 to line 30 in my flat BOM.
line 9 is at level 4 within the BOM - as its purchased - i want to ignore the next set of lines until i reach a part with a level less than or equal to 4 (1, 2, 3 or 4).
I want to apply this logic to all lines with the indented BOM.
A purchased item with a BOM can appear at any given level within the BOM.
I find the best method to understand the BOM structure is to look at one level at a time in sequence
Filter on levels 1 & 2 to see parent with relevant child, the look at levels 1,2 & 3. Then look at levels 1, 2, 3 & 4 and so on until you are looking at all levels.
Any help would be appreciated.

SampleBOM.xlsx