wp-admin: filter posts by custom field based on user login

I used CCTM (Custom Content Type Manager) plugin for WordPress and I created several custom post types out of it. In each post type, there’s a custom field named location.

I’ve got no problem with building the post types and its custom fields. But on the lists of posts in wp admin, I need to filter the items by Location – depending on the logged in user.

For example, there are 35 posts (from different admin users) with common location names (as set in the custom field):
20 posts = location is “Japan”
15 posts = location is “Korea”

When admin logs in, he should see all 35 posts.
When japan_admin logs in, he should see 20 posts only, those with location name as “Japan”.
When korea_admin logs in, he should see 15 posts only, those with location name as “Korea”.

Please help and share any idea on how to do this. I have searched a lot today and found no available plugin related to this. Might need to do wp hooks? Got no idea on how to do that either.

A newbie in wp here. Thanks in advance!