I have a data series on my chart for which I would like to plot a Linear Forecast Trendline.

a) I would like to plot this trend line only based on the last several (10) data points in the series. The trendline will forecast 8 periods into the future.

b) Ideally, I would like this forecast to operate as a sort of moving forecast (i.e. As additional data is added to my series it should automatically project the trend from the most recent 10 data points) without having to manually manipulate the parameters of the trendline.

Is it possible to due either / both of these in excel?

Thanks for any help with this!