How to Customize TABS CONTROL column of Summary Section in CRM 2011?

Hello,

I am learning  CRM2011 and working as a javascript and PHP developer. I just want to know can we customize TABS CONTROL column of Summary Section of a Case form.

Currently what we see,  in a case form  there is Summary Section and it have 3 columns

CASE DETAILS | TABS CONTROL | CLINET DETAILS

Note : TAB CONTROL is seen as protected (red lock sign )

when we open any Case it show 3 tabs in middle column

POST | ACTIVITIES | NOTES

I want to add one more tab near the NOTES, so will you please guide us how can we achive this?

Thanks.