Base Overrides locked out for editing after Sales history collection

We run a monthly forecasting cycle and forecast in monthly buckets.  After the forecast is generated for a month, users want to collect sales history on a daily basis so that sales history is continually updated on the worksheets.  However, this approach 'locks out' the Base Override from editing for the month.  For example, June 2011 forecast is generated and we have been collecting sales history on a daily basis. But we cannot update the June 2011 Base Override; we are locked out.

Is there a method or configuration that will allow us to collect the history in the current month and still allow base overrides?  I suspect the MaxSalesGen and Max_Sales_Date parameters will play a part in this.