My son asked the following question.
He washed and ate bread before shekia on Rosh Chodesh.
He is about to go to Maariv and remembers he didn’t yet Bench.
If he Benches now, he will be a few minutes late to Maariv. If he Benches later he will run into issue of saying Maariv without Yale Vyavoh and then he wants to Bentch with Yale Vyavo is a conflict….what should he do ?
This is a very interesting question. Practically the best thing is for him to daven maariv with a later minyan and bentch now (especially in E.Yisroel). Theoretically though it is a very nice question. I would want to say that he shold continue bentching because this is the mitzvah that he is in front of him fright now. However I don’t have any proof to this side or the other side, so for the mean time, we’ll leave it as a good question.