Set analysis 3 last months ItemQuantitySales

[PepeMontes]

Hi All dear experts,
I'm trying to analysis the quantity sold  of many items of the last 3 months form the current month with the next set analysis function but it's not getting any field:
=Sum ( { $ < Month = {$(=Max(Month)-1)} > } [ItemQuantity])
I would appreciate a lot if someone could help with this trouble, also i attached an example that show how supposed to look like.

ItemCode	ItemDescription	January ItemQuantity	Frebruary ItemQuantity	March ItemQuantity
1	Keyboard	106	70	62
2	Mouse	28	24	39
3	Headset	96	102	84
4	MotherBoard	4	10	7
5	HDD	229	130	143

King Regards.

JAMM.

[sunny_talwar]

How does your Month field look like... is it formatted as Jan, Feb, Mar... or does it look like 1, 2, 3?

[PepeMontes]

Hello Sunny,
As Jan, Feb, Mar.

Regards.

[sunny_talwar · Accepted solution]

How about this?

=Sum({$< Month = {$(=Month(Date#(Max(Month)-1, 'M')))}>} [ItemQuantity])

[PepeMontes]

it works, much appreciated thanks for your help and time.

Regards.