If the report has nothing in its Sorting And Grouping (View menu), you can
specify mulitple fields in its OrderBy property:
Me.OrderBy = "Field1; Field2"
Me.OrderByOn = True
More likely, you need to reassign the ControlSource of the GroupLevel in the
Open event of the report. Details in Andy Baron's article:
Sorting Records in a Report at run-time
at: http://allenbrowne.com/ser-33.html