>Can I achieve this? If yes, what are the commands? Thanks.

Maybe, is the best answer I can give you. I know it is possible using IBO
and I guess it ought to be possible with IBX.

In IBO, you get severe locking using tiConsistency as your transaction
isolation. I call it 'severe', because it is really not recommended. I've
never used consistency isolation, but I think it locks all records returned
to you. Locking a row isn't as dangerous a task, but make sure that it is
really what you want to do (IB is designed for 'optimistic' and not
'pessimistic' locking, and in general it is better to use what a tool
supports than try to defeat it). The way to lock a row, is simply to make a
fake change to it (e.g. UPDATE <table> SET <field1>=<field1> WHERE ...) If
you succeed in doing this, you know that no other current transaction has
done the same and that your transaction is the only one being allowed to
change this (these) records until you commit.

HTH,
Set