I recently wasted debugging time on a perfectly good macro. The problem
turned out to be Excel: when I manually changed a cell from a value that
looked like a number to another value that looked like a number, Excel
automatically converted the cell's NumberFormat from Text to Number. This
caused a routine that compares cell contents between different worksheets to
fail, because "0399" < 399.

I'm sure most programmers would agree that an application that reassigns
data types without warning the user is arrogant and inconsiderate in the
extreme.

Can I turn this feature off?