Instead of basing the subform on the table, create a query of the table. In the query design view go to the query's properties and find the TOP VALUES property. If you click its combo box it will show 5, 10, 25, 100, 5%, 25%, and ALL. You can type your own number there instead, so type a 3. As the name implies, it will show the Top 3 values as they appear in the query, so change the sort order as needed to get the most recent dates, the largest dollar amount, or whatever. Then set the criteria for the field that links the main and subforms together to
[forms].[frmMainFormName].[LinkingField].
Finally, place the subform on the main form and test it out.