Calculate required % by month to achieve target

[Shahria]

Hi Excel Masters. I'm working on a spreadsheet and i'd like some guidance how to build the formula. I have an end of year target of 5% (average) across 12 months. I want to create a table so when i input each month actual % it should tell me the required % for the remaining month in order to achieve 5% end of Dec. Hope that makes sense.