Sentiment analysis knowing emotion change position

Hello, I’m working on a project about digital human. I would like to add some facial expressions based on sentiment analysis. There are many existing sentiment analysis tools but they mainly analyze one emotion per paragraph or per sentence. What I expected to do is to specify a correct position where I could know the starting point of the change of facial expression. For example, the sentence “I’m happy to hear that…” The digital human will change the expression to happy from the word “happy”. I’ve done some literature reviews but feel a little loss. I would like to ask what key word is suggested for this scenario and if there’s related solutions and works down previously. I’m super grateful to any suggestions! Thanks!