Merge Pdf files using Macros

I want to develop tool to merge pdf files

1. Same Folder
D:\Pdf fiolder\
A.pdf
A1.pdf
A3.pdf
The file will be merged as A.pdf and stored into selected file path. N of files will be here. Merge logic should be file name start with same name

2. With sub folder
D:\Pdf files\Test1
A1.pdf
A2.pdf
A3.pdf
D:\Pdf files\Test1\Test2
A1.pdf
A2.Pdf
A3.pdf

The file will be merged from sub folder too, with same file name
That is, file merged with below file name
A.pdf
A1.pdf
A2.pdf