Add a pop-up menu to VBA

Today, I decided to upgrade my Excel account book to support more classification levels. The original drop-down list can only have one level, up to two levels have been very reluctant. This time I want to solve the problem by using the pop-up menu. Searching for information on the Internet basically achieves this function.
I feel that the most important thing is the help file of VBA. After downloading some documents, the help of a doc is basically useless, the object structure cannot be queried, and the attribute method cannot be queried, there is also a VBA for excel10, although it is CHM, the connection in it cannot be opened. Rummaging through the Cabinet, find the CHM file that was previously stored, and find a VBA for excel9 file. The content is rich and the problem is solved.
More and more Program Personnel, CHM help may be the most important thing, or even more important than the network. Recently I wrote web scripts, which are almost constantly written with the help of JavaScript and CSS. No way. JS is case sensitive, but I cannot remember the case naming methods of those functions.
These help are worth the following:
MapX help
Ado help
T-SQL help
CSS help
Javascript help
Sqlserver help
VBA help
......