John,
You could perhaps start with any old chart (X-Y scatter would be the
best) that has the same number of data points as the number of points
you are wanting to plot, then click and drag each of those point to
where you want them plotted. When you click on a marker it can be
dragged after it changes to an up/down/left/right arrow. When you are
dragging up or down the y value is shown in a box that pops up.
Similarly the x value when dragging left or right. You should also see
a line move along the y axis during up/down dragging. Similarly, along
the x axis during left/right dragging.
The values in the cells (source data) change accordingly.
Hope this is useful,even though I really don't know why you would want
to do it this way.
Ken Johnson