I have two worksheets in the same workbook that contain linked cells, a date.
The ones that contain a date in one worksheet copy the date into the other.
The problem is that if the "main" worksheet has cells with no dates the other
worksheet cells that should be blank fill with the value 00.01.1900 rather
than leave them blank as in the main worksheet.

Also the "secondary" worksheet says each of the cells needs to be locked
which I don't want to happen if I decide to change the date for any reason.