Actually, you can do this in both RS2000 and RS2005. In the chart properties dialog, edit the data point and select 'Plot data as line'. You can only do this with line combinations (e.g. not bar / area).
Don't expect this to be substantually changed in RS2005. The graphs haven't changed that much. As well, overlapping graphs won't be supported in a rendering engines, and will likely cause you additional grief.
Hopefully we'll see enhanced 3rd party support expanding in the coming months.
Chart combination
Pravin03
allroundmusician
Thanks for your answer,
IIMA
ert304
Hopefully we'll see enhanced 3rd party support expanding in the coming months.
Werdna
It is possible to overlay 3 charts with transparent backgrounds, but I do not think that the effect will be pleasing.
iowacbr600f4guy