Date named ranges not accepting Apr13 eg, having to use _Apr13 but pivot table not ordered

Hi

Please see sheets attached,

I am working on a financial year from Apr13-Mar14, im using named table ranges.

On my RS working sheet, i have 2 data validations, One column A which is the months picked up from the "Do Not Touch" sheet
The second is column D, which uses the Indirect formula.

The tables that are linked are found under the sales agents sheet.

That is all fine, until i try to use a pivot table to display the data. The pivot table will not order the months in the correct order, starts from _Jan14 instead of _Apr13.

I had to rename the dates to a _mmyy format, after i kept receiving errors when i was saving the workbook saying the name "Apr13" eg is invalid as excel already uses it.

Also it wont work even If i name the ranges as a mmm-yy as excel keeps reading it as a date which messes with the data validation

Please help how should I go about this