Prediction Sheet

Attached an example..please open and continue reading.

PrSales11 shows a list of product, each with their respective sales per month in 2011.
PrSales12 is another sheet which instead should have "predicted" figures - my idea is to simply take the values from 2011 and add a certain percentage..like for Product 1 in January.. the formula would be PrSales11!E4*1.02 (2%).

I need to prepare this for future proofing..so that means I cant really put PrSales11 in the formula.
I will have to get the current sheet name, PrSales12, concatenate and reduce 1 - so thus prSales13 will automatically link to PrSales12, and so on.

Please help me ot on this!
thanks

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