Since the key is only meant to indicate the column that should be sorted, it doesn't matter how you indicate that key:
.parent.Range("B1")
.parent.Range("B6")
.parent.Range("B1:B100")
.parent.Range("B:B")
.parent.columns(2)

Sub M_snb()
    With ActiveSheet.Sort
        .SortFields.Clear
        .SortFields.Add .Parent.Columns(2)
        .SortFields.Add .Parent.Columns(3), Order:=xlDescending
        .SetRange Range("A6:C19")
        .Apply
    End With
End Sub
The clumsy original code you retrieved from the help file in the VBEditor.