Activation of stock information tab fields in Equipment master

Hi All,

As part of our requirement we need to maintain sales order number in Equipment master to have link between them and to have trace-ability.However when trying to create Equipment master,stock information tab is grey out under serial tab.It would be helpful if anyone has any pointers on how to activate those stock information fields or atleast sales order & item fields under stock info tab while creating equipment master.

Thanks in advance.

Thanks

Amar