>>For some reason, I'm stumbling trying to figure this one out, so I'm looking for suggestions.
>>
>>We have a file of interest rates which we are currently indexing on:
>>

BankCode+DTOS(ValueDate)

>
>

BankCode+dtos(date()-ValueDate)

>

Nadya,
Subtracting one date from another gives you the number of days between them. As such, DTOS() will thorw an error because it expects a date not a numeric.