Adding title to date field (or similar)

Perhaps there is already a simple way to accomplish this but I am wondering about adding the ability to collect a title for a date field.

For example, I have need to be able to set up a date field in user accounts that collects the start and end date specifically for the user's Agent ID number, which can change. So I need the number of values to be unlimited, with a start and end date for each Agent ID. If I set up two separate fields, the Agent ID and the Date, they will display separately as such with no real association:

Agent ID (1)
Agent ID (2)

start date - end date (1)
start date - end date (2)

But I need the date and agent id's to be associated correctly so they appear as such:

Agent ID (1)
start date - end date (1)

Agent ID (2)
start date - end date (2)

Hope that makes sense. Being able to collect a title within a date field seems to be a good solution, if it is possible. I've add a visual mockup, hopefully for clarity.

Thank you in advance.