Merging Multiple Files

Hi Team

Howz all? As usual, a layman like me dont know much about excel have an issue. I have nearly around 12 excel files and I want to merge them into one sheet. I have googled the forum but didnt find what i needed. Im looking for a simple macro wherein all i have to do is run the macro and all the files will be merged into one without me opening any of the files.
Is this possible. can anyone help me.
Points to remember,
1. the columns will always be the same in all files
2. the data lines may vary. In the sample file attached, Ive only put one line data but in reality there will be more than 20000 lines per file.

Any help..