AuditStage - Validation of Date Fields

[caharris]

We have Date fields stored within a SQL Server 2000 Database in the char format YYYYMMDD. I am trying to confirm that the data is in fact a valid date from within a Data Filter.
When I set the TypeofCheck to TYPE and set the Reference Data field to DATE the sql syntax generated becomes ISDATE(fieldname) which is a valid function within SQL SERVER. However, I am getting an invalid SQL syntax error and even if I translate the syntax into Query Analyser it wont run. Any suggestions or alternative ideas?