Dynamic chart (moving in time)

I am strugling to find the most efficient way to create a chart I need. It is supposed to be a forecasting tool and I want the chart to change as time goes by.

As an example: We are now in May. Let's say I have actual sales data for Febryary, March and April, in addition I have forecasts for May and the following eight months (12 months total). As May is coming to an end I will soon have actual data for May as well. The actual as well as the forcast data will be manualy registered, but what I want is a chart showing me the three months prior to the current month of actual sales data, plus the current month and the following eight of forecasts. How can I make the chart work in such a way that it will change to always stay updated with three months of actual sales data (prior to current month) and nine months of forecasts (current + eight future months)?

To exemplify further:
If the month is May 2012 i want the chart to show:
February 2012 - January 2013; February - April actual sales; May - January forecast sales.

If the month is June 2012 i want the chart to show:
March 2012 - February 2013; March - May actual sales; June - February forecast sales.

etc. etc. etc., and I want this change in the chart to happen automatically, of course, given that the input data of actual and forecasts have been entered.

Is there a way to do this without involving VBA programming?

Thanks in advance!

Attached you find an example of what I am talking about. The chart shows three months of actual sales data and the nine following months of forecast data. As it is now, the changes need to be made manually. What I want to happen is to somehow make the chart move range from mar.12 - feb.13 to apr.12 - mar.13 when July comes around, then August, etc.

Data in the Actual and Forecast columns should always be up to date, perhaps with the exeption of the 1st of every month when it comes to Actual data for the preceding month. Additionally, it would be great to just register the Actual and Forecast data in a historical manner and have the chart "gather" the information from there. This way I will always have the historical record, but a relevant and clean chart to look at.

I guess there are many ways of going about this issue, but hopefully there is a solution.

Thanks in advance!

Edit: I added data to Sheet 2 as well. Stepping from Sheet 1 to 2 shows what I want to happen when the month changes from June to July. Naturally, I would have to provide the Actual data for June manually, but the change in the chart is what I want to happen automatically.