There are two mutually exclusive questions here for one birth time. Seen is certainty, and not the same as possible.
What are you asking? Are you asking if there is a certainty that this person will ask you to marry him? Are you in a culture where this is an arranged marriage? Are you asking if it's possible that he might ask you? Are you asking if you will say yes?
Horary Astrology needs four things:
1) it has to be a personal question that only you would ask. If other people can ask it then you would have possible multiple birthdates for the same question,
2) It has to be a question that your actions are not the primary ones that make it take place. You cannot second guess yourself; you cannot ask what you wlll do.
3). It has to be a question that can be answered in a yes/no fashion. More can be known than yes/no, but asking a who-what-when-where is not a horary question, its an Event Astrology Question(what happened here?),
4. It has to be something that will happen in no later than 6 months, but preferably no later than 3 months. After 6 months certainly of result drops quickly to a 50/50 chance of being correct.