I have data in a chart. I want to set up a macro to perform calculations on
this data, but I want to be able to select the "starting point" - which will
not necessarily correspond to the first data point.

Is there a way to allow a user to manipulate a "line" on the graph so that
where they position that line (along the x-axis) will correspond to the
starting position to perform calculations on the data?

Any other suggestions?

Thanks
Frank