Read level locking for mysql

[lata rishi]

Hi,
I require a solution for the following problem in mysql.
Like a reservation system, when multiple users are working on the same database for read lock and then update records.

One user/thread want to select some records from a table, do some operations on them.
Parallely another user also want to select records from the table, but not the one selected by first user.

How i can achieve this in mysql?

I tried using Select .. with update, but it works in the transaction mode.

Thanks
Lata Rishi