This method returns currently selected text. If Index
argument is not specified, then full selection is returned,
split by VbCrlf (CR+LF) sequence.
If Index is selected, then only n-th row is returned. No
matter which row is selected (for example, selection spans
from row 3 to row 10), Index = 0 will return 1st selected
row (row 3 in this case...).
Setting this property to anything will clear out
current selection, and argument passed to this property
will be ignored.