problem in execute dynamic SQL statement.

We use Informix 4.10.UE2 version on IBM RS6000 with AIX opearating system. We found a problem in updating records with a where clause and one of the columns in the where cluase is null. We set the sqlind to -1 for the where clause column that has a null value, but it does not seem to update the records in the database. But if we set sqlind to -1 for the where clause column that has non null value, execute using descriptor statement seem to work. But not if the value in the database is actually null. If anybody has any solution send email to shyam@minerva.robadome.com Thank You Shyam