RightAngleAxes Property [Excel 2003 VBA Language Reference]
True if the chart axes are at right angles, independent of chart rotation or elevation. Applies only to 3-D line, column, and bar charts. Read/write Boolean.
If this property is True, the Perspective property is ignored.
This example sets the axes in Chart1 to intersect at right angles. The example should be run on a 3-D chart.
Charts("Chart1").RightAngleAxes = True