In Excel 2003, it's possible to change the z-order (i.e. what plots on top) of data series plotted on an axis by right-clicking a point of one of the series, choosing "Format Data Series", and then using the "Series Order" tab.

However, I've got a plot with series on both primary and secondary y-axes. While I can change the relative z-order of series plotting on the same axis, I'd like to alter the z-order so that my series plotted on the secondary axis plot "below" those on the primary axis.

Excel's default behavior appears to put secondary-axis series highest in z-order. Is there a way I can alter this? Excel, VBA, or any other solution welcome!

Clarification: by z-order I mean this---imagine that each data series is drawn on a transparency, and the transparencies are overlaid to produce the complete chart. Z-order is then the order in which the transparencies are stacked. In other words, when two series intersect, the appropriate color for the series with the higher z-order should be drawn at the intersection point, and the other should be suppressed.

I am not referring to the vertical (i.e. y-axis) placement of the series; I'm completely aware that this depends upon the selected scale.

Z-order may not be a commonly-used term outside the 3-D graphics/rendering community. My apologies for any confusion.