Excel can handle 64,000 records per sheet. You can have up to 256 sheets I think but scanning over sheets is a bit harder.
I suspect that is way more than you will be able to manually transscribe from hand written records in any forseeable timeframe.
If they had been typed records you could have used some Optical caharcter Recognition software (Adobe Writer or the like) but hand written is way harder.
I would suggest getting a subset, say 100 records, and playing with that to get the format and functionality as you want it before you go too far down the data entry route.
Think about codes and groups as seperate columns so that you can manipulate them later. e.g. A date with text on a field can not be sorted on. A date as a seperate field can be sorted.