Report Filter Expression Based On DATE, But Limited To 12 Months

I'm trying to find out how to add a filter expression on a report for Sage 50 Accounts, such that the report only looks at GDN_ITEM_DATE that is from the last 12 months from the CRITERIA.GDN_ITEM_DATE_TO specified when the report is run. I then need to return a string from the GDN_ITEM_DATE based on the month value, i.e. if CString(MonthFromDate(GDN_ITEM_DATE)) is 3, the value displayed is "March" etc... Unfortunately for me, our financial year is July to June, so month 1 is July etc...

Example,

Todays date is the 15/06/2016. On my report, I choose the report CRITERIA.GDN_ITEM_DATE_TO as 30/06/2015. I'm only interested in GDN_ITEM_DATE with a value between 01/07/2014 and 30/06/2015, as that is the 12 month period preceding the CRITERIA.GDN_ITEM_DATE_TO chosen date. Having got the GDN_ITEM_DATE, then I need to display July ( 07/2014 ) first, then August ( 08/2014 ) through to June ( 06/2015 ). The data created, will then be used for creating a Pivot Table in Excel.