I would First Create a table called Months and Fiscal Years. There would be 4 fields: Month, Year, Fiscal Year, Last Day of Month (date field)
Preload this using an Excel Sheet import, for the next 10 or 20 years.
Use a relationship where One Month and Fiscal Year has Many of your Current table.
On the current table, Make a formula that simply extracts the fiscal year from your Posting Date=Fiscal Year in New Table. Then use a conditional dropdown to only show the pre-loaded entries where Fiscal Year from Posting Date. The report you would use would have a filter Last Day of month>=Today(). This would eliminate all the past months.
------------------------------
Mike Tamoush
------------------------------