WEll, i apologize for not responding. i was pretty ill n just got off the bed. well i know about what ROM is. BUT thanks for "enlightening" me. about the hardware i am pretty good at it. i dont know where the heck did this assumption creep up.
well the need for using the RAM as code memory is the Requirement that once the product that i am developing does eventually ship to the users, then the users have the option of using new applications as they are developed. for doing so they will only need to place the hex file in the MMC card rather than reflashing the ROM. which is normaly the case.
the flow is like this.

there is a RTOS in the ROM, with FAT, MMC interface and keypad and lcd driver, calculator and few other applications. all this is done.
now a ram has been integrated the requirement is the anticipated ability of reading hex code from mmc and then writi ng that hex file to the External RAM. this will require the RAM to be used using as data memory. now the need is to switch control to the hex code that has been written to the RAM. for doing this the External Ram that was being used as data memory will now need to be treated as code memory.
i hope i have made my point. i thank you all for taking time out to help me. i am trully indebted and encouraged to find such a helpful lot. :)