Excel 2007 : Estimated vs Actuals

Hi all,

I have a demand forecast sheet in place which shows estimated sales from Jan to Dec. Monthly, I will export sales figures into actual columns.
I want to know if it is possible that when the actual column for example in January is updated, the value shows up in "est vs act" tab overwriting forecast value.

Is it possible to do that or do I have to insert the value manually every month?

Thank you for your advice.