In this case, the Combo box would be the preferred way to do it.
Create a combo that has two columns, the unique employee id (should ususally
be the primary key field for the employee table), and the employee name.

Now, here is the good part. You can use the combo to filter your report.
Don't put any filtering by employee in the report's record source query, do
it in the OpenReport method.  If the combo is set up as suggested, the combo
will return the primary key value for the selected employee.  You then use
that in the Where arguement of the OpenReport method:

Dim strWhere As String

   strWhere = "[EmployeeID] = " & Me.cboEmployee
   DoCmd.OpenReport "rptEmpReport", , , strWhere