Formatting A Number Field To Hold A Specific Number Of Digits

I wrote an excel program in Excel'03 for a dental office to manage state assistance patients and one of the table columns is the state assistance number. The problem is that the program defaults to a number format when it is entered instead of a text format, which is what I want. The issue is that state assistance numbers are always 8 digits and when it defaults to a number field the program drops the required preceeding zeros.

For example the number 00123456 will sometimes show up as 123456, which is wrong. It's like sometimes it will show up right and other times it gets a butterfly in its brain and deletes those zeros irritating the receptionist here. So, how do I get the table to either stay in text format or set up a number format that keeps the preceeding zeros?