CC2530: Writing IEEE secondary from code

Hi,

I am trying to use the code below to change the IEEE secondary value from a program

uint8 new_EXT_Addr[Z_EXTADDR_LEN];

new_EXT_Addr[0] = 0xB6;
new_EXT_Addr[1] = 0x00;
new_EXT_Addr[2] = 0x00;
new_EXT_Addr[3] = 0x00;
new_EXT_Addr[4] = 0x0d;
new_EXT_Addr[5] = 0xaf;
new_EXT_Addr[6] = 0x80;
new_EXT_Addr[7] = 0x05;


HalFlashErase( HAL_FLASH_IEEE_PAGE );
while (FCTL & 0x80);

HalFlashWrite(HAL_FLASH_IEEE_PAGE + HAL_FLASH_IEEE_OSET, new_EXT_Addr, Z_EXTADDR_LEN); // reads secondary IEEE address

however it is not changing the value. 

Any advice on changing the value would be appreciated

Thank You