I'm plotting timed events against a set schedule (actual lap times vs
predicted times) and am calculating the difference and plotting the
results.

In Excel 2003, I would use the 1904 Date System (Tools, Options,
Calculation tab) to display negative time values and then force the
chart to link to the source data to determine the format. It would
display positive and negative time values on the y-axis

In Excel 2007, changing to 1904 date system will show negative time
values in the spreadsheet AND will plot negative points on a chart,
but WILL NOT DISPLAY NEGATIVE TIME VALUES ON THE Y-AXIS. Using fixed
or auto scaling has no effect.

Does anyone have a solution for this?