Selecting up with a mouse in vim

[TheQuirk]

When I do :set mouse=a, I can drag the mouse down to select text below the current bottom line (vim just scrolls down). I can't do the same when I drag my mouse up. Is there any way to change this behavior?

[Basher52]

If you mean that when clicking the last charcter on the last row in vi/vim then want to mark text upwards in that file it starts scolling "the old text" that was shown before you got into the file? I also get that
And how do you do this 'set mouse=a' if you mean that this will scroll the vi/vim-edited text down so you can select rows below the last one you see? 'cos I got big problems selecting all rows that way.

[Basher52]