One Query To Return Either Records Within "Date Range" Or "12-Month Rolling"

I have a query that selects usage records from a table where a data field falls within a rolling 12-month period that ends on a month and year selected by the user on a form.

PARAMETERS [Forms]![frmReport]![cboMonth] Short, [Forms]![frmReport]![txtYear] Long;
SELECT UsageID, dtUsage, dblUsage
FROM tblUsage
WHERE (((DateDiff("m",[dtUsage],DateSerial([Forms]![frmReport]![txtYear],[Forms]![frmReport]![cboMonth],1))) Between 0 And 11));

I also have a query that pulls data between two dates that the user specifies using two textboxes on a form.

SELECT UsageID, dtUsage, dblUsage
FROM tblUsage
WHERE (((tblUsage.dtUsage) Between [Forms]![frmReport]![txtStartDate] And [Forms]![frmReport]![txtEndDate]));

On the form I have an Option Group control that sets the visible properties of the 4 controls;
12-Month Rolling
cboMonth - Month Combobox
txtYear - User entered year
Date Range
txtStartDate - User entered Start Date
txtEndDate - User entered End Date

What I was planning on doing was adding two new textboxes (txtQryStart & txtQryEnd) and depending on what option is selected, change the dates accordingly

blnDateRange = (Me.optDate = 1)
blnMonth = (Me.optDate = 2)

If blnDateRange Then
Me.txtQryStart = Me.txtStartDate
Me.txtQryEnd = Me.txtEndDate
End If

If blnMonth Then
If Me.cboMonth = 12 Then
EndMonth = 1
EndYear = Me.txtYear + 1
StartMonth = EndMonth
StartYear = Me.txtYear
Else
EndMonth = Me.cboMonth + 1
EndYear = Me.txtYear
StartMonth = EndMonth + 1
StartYear = Me.txtYear - 1
End If
Me.txtQryStart = DateSerial(StartYear, StartMonth, 1) - 1
Me.txtQryEnd = DateSerial(EndYear, EndMonth, 1)
End If

Now I can use one query to accomplish both types of query;
SELECT UsageID, dtUsage, dblUsage
FROM tblUsage
WHERE (((tblUsage.dtUsage) Between [Forms]![frmReport]![txtQryStart] And [Forms]![frmReport]![txtQryEnd]));

This approach works. It saves me from having to duplicate the queries and some future headache if anything needs to be changed in the queries.

What I was wondering is there an better/simpler way to do this?
:confused: