Acc. Sched. to see same period last year -1Y not working

bgadhvi1

I seem to have a problem with checking the same period last year in Account Schedule. I'm fairly new with NAV so any help would be appreciated. I've created a column in column layout called 'Difference Last Year' with the coloumn type as 'Net Change'. Within the 'Comparison Date Formula' I've put in '-1Y'. Now when I filter on the date, for example, '01/01/11..30/04/11', I dont get the correct figure in the 'Difference Last Year' column, it gives me the figure for the entire year last year, not the period I've filtered on. If I use the pre-defined periods of 1 Day, 7 Days, 1 Month, 3 Months or 1 Year, it works fine, but not when I specify a certain date in the filter which doesnt correspond to these pre-defined filters.

Any help is much appreciated!!

Bhavesh