distinct count an sum for 3 periods in chart

[#1]

Hi guys,

I have one interesting task which blocked me . In attachment you can see table with data and chart which calculates unique CaseId by each period (count1) and appropriate sum of amount (sum1). But I must calculate unique count of CaseId for last three periods (for example, period 2012-08 (dimension) should show count of unique Caseid for 2012-08, 2012-07,2012-06 periods, if 2012-07 doesn't exists that means for this periods goes 0). As also I must get sum of amount for last three month. The desired result you can see in result.jpg file.

Thanks for any help.

[#2]

ehhh,how i understand, noone has idea how to realise it.