Empty cells in lists

Hi, I'm new to the forum, my name is Eduardo from Monterrey (México). Thank you in advance for your help!

I have the following set of data:

Forum1.png

It is a list of researchers in Mexico, it is sorted by University, Department, and Academic Group (AG, in the image is the column labeled as CA). Every AG have a variable number of researchers, and the original file only write the AG for one of the researchers (the first one of each) and the other ones does not have this information in its respective column. So, if you use a filter to have the names of every researcher interested in, e.g. pharmaceuticals synthesis, if there are 100 researchers distributed in 20 AG, there will be only 20 researchers that have the specific AG specified in its column, so the other 80 will be impossible to find if it is not made manually (one by one). Since there are not 100 researchers but more or less 15000, then the work cannot be made manually.

The question is: how can I fill the empty cells with the value that corresponds, for example (in the image), D5:D15 with the value in D5, then D16:D23 with the value in D16, and so on.

I hope you can help me.

Thank you in advance!
Best regards
Eduardo