What advise can you give us if the data is already in a spreadsheet??
Not much. If the data is already in the spreadsheet as numbers, the 5 digits are already lost. This kind of thing has got to be taken care of when the data is imported/entered into the spreadsheet. If Excel is importing from a text file, you need to instruct Excel to treat the data as text and not number. If the data is brought into the spreadsheet from a macro or program, then the macro or program needs to be programmed to put the data in Excel as text.

Can you better explain how the data are being entered/imported into Excel?