How to add moving average to Report Builder 2.0 chart

This is driving me nuts. I've looked at all the relevant MSDN tutorials but they talk about 'data field drop zones' and how a 'Add Calculated Series' menu option should be there but it's not, and no screenshot is provided to show what a 'data field drop zone' is. This is the menu I get when I "right-click on a field in the data field drop zone":

The frustrating thing is I know I've seen this calculated series stuff before, but I can't find it again, it's not in the 'Series Properties' dialog that I can see, and I can't find a tutorial showing how to find this feature. I'm guessing you can only have a calculated series on certain chart types, or I don't have some flag turned on or something, but I didn't see that mentioned anywhere.

Can you tell me how I can add a line showing the median of my data to a chart in Report Builder 2.0? I think I can do this by adding a 'Moving Average' via a 'Calculated Series', but I can't find how to add that.

Edit: on a different chart, the 'Add Calculated Series' me开发者_如何学Gonu option was available. It was a stacked column chart and the series I right-clicked on was an expression that used RunningValue.

I had to remove the series group (from the 'data field drop zone' on the right side of the chart) so that all I had was 1) a category group (bottom of the chart) and 2) a data series (top of the chart). Then I could right-click on the data series at the top of the chart and 'Add Calculated Series' was a menu option.

I solved it by making the groups as individual series and then a combined series that i set to hidden. I was then able to make the calculated series from the hidden series.