Don't allow user use worksheet if cell is not filled

Hi all!
Here I have a table which is to be filled in daily. Especially last column. But users sometimes ignore it. Would it be a possibility to make some kind of formula saying "hey, if you don't fill this cell in the last column, I won't let you do anything in this spreadsheet". A?

Thanks guys in advance!

Well, thanks, but I am new in VBA. Actually I am looking for formula, not for VBA code. The project is to be used by my boss, and if something will go wrong with the workbook, I won't be able to explain as I don't know VBA at all.