migration - domain local groups in target domain

hello,

i'm preparing an interforest migration and so far everything is going well
(users, groups, gpo's...)
but i have one question regarding domain local groups in my TARGET domain
(=our main one) that contain users/groups from the SOURCE domain (=the one
that will be discarded).
Is there a way to automatically re-map the old SOURCE entries to the new
TARGET entries that have been migrated?
afterwards i would also change the group into a global one. there is a two
way trust relationship between the two domains.

example:
"dom_loc_group_XYZ@TARGET_dom" contains "userABC@SOURCE_dom"

but since i've done the user migration, "userABC@TARGET_dom" also exists.

so how can i change/edit/migrate the old "userABC@SOURCE_dom" to the new
"userABC@TARGET_dom" in the "dom_loc_group_XYZ@TARGET_dom"? (without having
to do that manually, group by group)

i thought about a migration table or something (as with the migrating of the
GPO's), but don't know where or how to implement it i this scenario.

regards,
Steven.