Authorizations for creating Purchase requisitions and Purchase orders.

Hi,

I set a release strategy for all purchase orders and purchase requisitions having

particulars "Purchasing group".

Now I would like customize the system so that only specific users (user name)could create purchase orders and purchase requisitions.

So if a particular user try to execute ME51, ME51N, ME52, ME52N, ME53, ME53N, the system will not allow the access to those trx.

How about?

Thanks in advance