Excel Auto Fill – How to Fill Over 10,000 Rows in Excel Without Dragging

I have more than 10,000 rows of data I need to do some calculations on one column of the data. I have made the calculation in one cell and now need to fill the formula for the calculation and all the cells.

Usually I just select the cells using the keyboard and then press the Ctrl+D to fill the cells. However, now I have to do this repeatedly, and it is difficult to keep on selecting 5000 rows each file. Is there a simpler way where I can just specify the range using the keyboard? Perhaps even have a macro since all of the files have a fixed length

Also, since I have difficulty in using the mouse because of medical reasons and therefore I have not tested this particular solution which involves clicking on a very small fill handle. Maybe there is a parallel solution to this using the keyboard or maybe I can create a macro which will automatically click on a fill handle of a selected cell – please advise if there is a way.