Data eeprom code protection bit 18f67k22

hI GUYS , i am trying to set the data eeprom internal to be able to externally read , but not externally write , however it appears that by setting the CPD bit stops external writes and reads

setting the WRTD bit stops internal and external writes

if i reading the setting correctly the WRTD bit would stop any writes by the internal program to the eeprom and i dont want that so settng this bit would not help solve the read only external , no writes external ?

there is no setting to do what i want - microchip confirmed

there might be a clue here
http://www.microchip.com/forums/m24540.aspx

and I'm sure I have seen a dt thread somewhere about writing to the config word regs on the fly , but I can't seem to locate it