Right click each series and set the chart type property of the series
seperately.

alas wrote:
How can I get a combo chart with 3 series - one as a vertical
bar/column, and 2 series as lines, with 2 y axes?
I only seem to be able to get one series in line format, while the
first two insist on viewing as vertical bars, regardless of whether
they are assigned to the primary or secondary y axis.