Hello and welcome.
Here's what I think you need:
You need to show information from table B when data is changed in a field in table A. For example, if I type in a certain genre of movie, I see many movies that fit into that genre. If I change the genre to another type, then different movies are visible. Is that correct?
To do this you have to explore the idea of using portals and global fields in a relationship. If you've never used those before, I suggest looking through the web for those ideas.
Here's a very brief description:
A portal is a window into a related table on a record. If the record has the genre "horror" stored in a field, then you can view the movies in table B that are horror in the portal. This is accomplished through the relationship.
To make the portal change its contents while on the same record, a relationship is set up to table B using a global field. Global fields do not store their data. If you have a relationship to table B from TableA::GlobalField = TableB:Genre, then any value you type into that global field will relate to different (or no) records in TableB. Thus, in the portal, you'd see the list of movies change.
Is that what you're looking for?