The program which first locks the table has usually the type set up. If it is not Your program, You surely are not able and allowed to modify the standard locktype, which was set up, at runtime. As far as I know.
If it is Your program, then You can self define, which lock type You can use.
http://www.sapdev.co.uk/dictionary/lock_enqueue.htm
will tell You about the types and a code sample in the link should provide all information, which You might need.