How to Disable the Push button in CRM_BSP_FRAME

Dear Experts,

In the BSP application "CRM_BSP_FRAME" i want to Disable the Pushbutton "NEW"

according to the User i.e For Few Users it should be Enabled and for the Few Users it should be Disabled.How to Do this Could you please send me the Document.

It is very Urgent Requirement.Please help me to solve this Problem.

Thanks in Advance.

Regards,

Ashok.