Every button could call a procedure like:
Code:
Private Sub SortForm(Byval FirstLetter As String)
If Len(FirstLetter) > 0 Then
strFilter = "SomeField LIKE '" & FirstLetter & "*'"
Me.Filter = strFilter
Me.FilterOn = True
Else
Me.FilterOn = False
End If
End Sub
It's very difficult to be more specific without knowing anything about your database.