Cells hold their values once data is deleted

Hi,

I'm putting together a spreadsheet that involves a weekly forecast for month end position where data is inputted and then subsequently replaced the following week. Is there a way (other than pasting values over the forumlas), to retain the output from formulas even when the data has been deleted? Some of the users of the workbook are not entirely confident in Excel so I would like to reduce their required input where possible.

When the new data is entered it overwrites the previous forecast.
Week 1 -80
Week 2 -80
Week 3 -80

I'd like to be in a position where the previous forecasts are held in the spreadsheet (despite the historic data no longer being there)
Week 1 -50
Week 2 -75
Week 3 -80

I don't have much (if any) experience with macros, but will be willing to give it a go if needed! Any ideas?

Thanks,

Matt

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