Display multiple Y-values for the same X-value in a line/symbol multi-series graph

I have XML measurement data containing expected and measured values, whereby the expected values can occur more than once: the measurement process calls for the expected values to be increased and then decreased, then possibly increased again.­…

When I display the measured values as a Y-axis series in a line/symbol multi-series graph against the expected values on the X-axis, it appears that only the latest measured value is shown for a given expected value.­

Is there any way to force all the measured values to be displayed?

I would have liked to have all the values on one graph, but if there is no way of doing this then I will have to generate two or three separate graphs.­­