Sounds like when you are deleting the input data, you are also deleting the formulas that are being used for the calculations!
TBH, when the Workbook was set up, it should
have been done with the individual Worksheets protected, and the cells with the formulas in should be locked to prevent deletion. Better still would be a macro to delete only what was required to start over.
I'm a self confessed Excel nerd and happily spend hours working on automated solutions to instances where manual input would be much quicker, just because I can
I'm happy to take a look at your Workbook if you want to send me a copy. If you do, save is as .xls though (2003 format) as I am steadfastly refusing to move onto 2007 or 2010, as I hate the ribbon! Anything I can do with it will be compatible with what you are using!