Could you make an additional secondary data source (retrieve values type) and ask it to retrieve the values from the table with the user names and the dates? This would be ok for an SQL database - not sure on Sharepoint.
Then set a filter on the secondary datasource which is based on the currently selected value of the user name and requery it when suitable.
The secondary data source will contain the dates for that username. You could try one of these approaches - further adjust the filter for something like 'AND position() <= 3 or use conditinal formatting on the repeating section/table display to hide when position() > 3.