PLEASE PLEASE PLEASE Help Me!!!

This one has got me baffled - can anybody please help me ... I am using Informix v4.00 RDS, I4GL and ISQL. Is there any way of assigning a NULL value to part of a column value ? For example, I have a column in a database table which is 28 characters long. I need to insert a value into the first 4 characters whilst leaving the remaining 24 characters as NULL. If I use a command similar to: let recordname.keyfield = "1234" and insert the row, the remaining part of the field is written as spaces. I have tried assigning a program variable to null and building up the field value as follows: initialize null_field to null let recordname.keyfield = "1234", null_field but this makes no difference. I have also tried adding a NULL record to the database and using SQLCA.SQLERRD[6] to obtain the rowid of the new record. Then update the table setting keyfield[1,4] to "1234" where rowid equals the rowid of the newly inserted row. Unfortunately, this doesn't make any difference either. The reason I need to do this is because I am writing some software which integrates with another 3rd party package. This 'other' package recognises record locks by assigning the last 24 characters of the keyfield to NULL. Although I can check for this using SQL similar to: select keyfield from table where keyfield[1,4] = "1234" and keyfield[5,28] is null I cannot seem to use 4GL code to make similar locks which would be recognised by the 'other' package. Any sugestions would be greatfully received !! Regards, Keith. *************** tech@compsys.demon.co.uk *************** Tel: 044 (0)1482 803961 Fax: 044 (0)1482 804333 ********************************************************