You wish to monitor certain files for change in hash / checksum / MD5 values and provide the changed i.e. the new hash value of modified item in the event
We can configure the detection policy to monitor file checksum ; While configuring the detection policy, please ensure the checksum option is checked.
If this is done, the event generated does provide the old and the new checksum in the event generated.
Please refer the attachment where test.txt file in C:\ is used as an example.