I have a spreadsheet which has some complicated formulae in some cells, so I
want to lock and protect those cells to prevent other users from spoiling
them.

However, one of the things these users need to do is to insert rows to add
new data in the correct place. I would like the formulae from the
corresponding cells above the new row to be automatically copied. The only
way to get the formulae in that I know is to use the "fill handle" but you
cannot do that when the cell is locked.

Is there another way?