HELP! Selecting and locking rows in a transaction

I'm using Informix 4.00 on SCO UNIX System V/386 and I have the following problem: within a transaction I need to select some records from a table (in a database created in MODE ANSI) and lock them in exclusive mode to avoid that other users modify these records until the end of the transaction. My test contains this 4GL code: SET ISOLATION TO REPEATABLE READ DECLARE jcurscab CURSOR FOR SELECT columns FROM table WHERE condition FOR UPDATE FOREACH jcurscab INTO record[].* .. .. END FOREACH wait for user input COMMIT Using the code in two different programs with different condition I noted that if one of them is blocked waiting for input another copy of the program the SELECT fails with error -243. Do these statements lock all the table or just the rows that satisfy the condition ? How do I lock ONLY the records that match condition ? Thank you for your help.