>When updating SQL Server database with a duplicate value in a unique column I get error 1526 (using VFP function
>AERROR(aErrorInf )). This number seems to be specific to SQL Server and not to VFP. Does it change from version to version of SQL? The reason I am asking is I want to "translate" this number into a meaningful message to a user.

If that is ODBC error AERROR() returns this:
1 Numeric. Contains 1526.
2 Character. The text of the error message.
3 Character. The text of the ODBC error message.
4 Character. The current ODBC SQL state.
5 Numeric. The error number from the ODBC data source.
6 Numeric. The ODBC connection handle.
7 The null value.

Run this in SSMS:

SELECT * from sys.Messages WHERE Language_Id = 1033

And you will get all error messages SQL Server returns in English.