I'm simply interested to see among 20 countries I have, which one's where more successful in publication during the past years.
In many ways, it seems like your question really isn't about Excel (yet), but more about how to measure "success" in publication. If I am wrong and you do know what metric you want to use to measure "success", then explain that metric to us and we should be able to help you program that metric into Excel.

If this is more about determining what metric to use, I might suggest that we start with some of the simplest metrics:

1) Total publications. In Excel, this would be a simple =SUM() function. Of course, the question of "most successful" is "which country has the most publications?" -- A simple =MAX() function in Excel.

2) "Total publications" may be confounded by other variables. Populous countries or wealthier countries may have a natural edge using this metric. Perhaps a better metric would be "Publications per Euro spent" or "Publications per researcher" or something similar.

3) Since you introduced the idea of using "regression" techniques to this, this perhaps suggests that "more successful" is more about how each country has changed over the last 20 years, rather than total measures like the previous 2 metrics. The challenge here is that you need to choose your base metric, and then choose how to measure "change".

Just a few thoughts. Once you choose a suitable metric to measure "success", then I think we will be better able to suggest algorithms and spreadsheet programming to implement those algorithms.