I as with many others seem to have a problem with this.

I have a table containing data for four years (monthly) and not all the data starts and finished at the same time period. Using a lookup selectable by user I am able to plot the data for one series against the average. Removing the references prior to the start and after the finish is okay, however where I am stuck is where there are gaps in the series which should not be plotted. If plotting the series manually it is okay as the values are null, but using the lookup feature excel treats the formula itself as a non null value. I would prefer not to use VBA but cannot find any way around this at present.

Any comments would be appreciated