I'd like to have a date entry that I make in one cell (range named
YTDDate) be duplicated in another cell (named DealDate), without using
text boxes from the Forms or Control ToolBox, or at least anything
visible. In other words, to the user, the spreadsheet should look
unadorned, and when he enters the date in YTDDate, the DealDate cell
is similarly updated.

I seem to recall there was a way to do this through buttons that were
made invisible, which essentially triggered a macro.

If the above step is not possible, I'd also like to ask if there is a
way of triggering an input box macro when the cursor is placed on the
YTDDate. This input box would ask for the YTD date, and on OK, it
could write th same date to the DealDate cell.