incremental MD5 ?

hi everyone!!
i'm writing some program that backup memory data.

and i'm trying MD5 encryption, the original data is quite big and MD5
encrypted data is added to it..
it is like this


----------------------------------------

original data

----------------------------------------

MD5 encrypted data (of original data)

----------------------------------------

and after reboot, it read memory data and encrypt it, and compare it
with previous encrypted one.
if it is different (maybe spoiled, damaged), then find different part
of the current data, and recalculate the part with MD5,
and update MD5 encrypted data on the exact part of it...i mean, update
only exact part of encrypted area...

do you think MD5 can do this method?
do you think the whole data's encrypted data is same as previous
partially updated one?
incremental MD5 is implemented ?

.