A couple of things. Just as a best practice always be explicit in your field names (prefix with table.) Use brackets in all the references. Also remember that ADO wild cards are "%" & "_" instead of "*" & "?". Finally if you are using a wildcard you will need to use the LIKE keyword. I suspect this should work for you:
[VBA]SELECT * FROM [rep1] where [rep1].[casetteID] LIKE '_';[/VBA]