Splitting up one's highlighted selection as if you had used to"control" button for each selection
 

I'll make this simple.

Let's say I hightlight, say row 4, of a spreadsheet by clicking on the
actual 4. I then push control, shift, and down arrow at the same time
to highlight all the rows.


How do I quickly change my highlight to as if I had pushed "control"
button and highlighted each row individually.

I know that you can use F5 when, say, subtotaling and click "visible
cells only," but really this is different because the rows may be
continuous.

I need to do this to make Border changes to each row where the rows
may or may not be continuous as far as visible cells go.