I am trying to edit the data range for a series (5 non-adjacient cols x 400+
rows so clicking on the select cell block is not really an option, I just
want to change the last cell from x400 to x407).

When I use the arrow keys to move to the end of the input field, it inserts
the address of a cell behind the graph.

How do I move the edit point without using the END, or arrow keys(which
insert the current, of new addres of the "cell pointer")? OR
How can I resize the "Edit Series" box so I can see the complete text and
then use the mouse to select the cell number I want to change?