Accessing multiple files with variable names

I have 4000 files with variable names based on the latitude and longitude of places (in the form: data_lat_long). I want to import these files and add the corresponding values present in the 4th column of each file. Can you please provide the code for the same??

[Jan]

We cannot guess, how your files must be imported. What does "add the corresponding values present in the 4th column of each file" mean? What is "corresponding" with what? Do you want to create a sum or to add a column in the files?

Where are the files stored? All in one folder or distributed over a folder hierarchy? How can you obtain a list of the file names? What does "with variable names" mean? That the files do not have the same name?

Please explain much more details and post, what you have tried so far. If you ask a specific question to the existing code, a useful answer is more likely and the process of assiting you is much more efficient.