Analysis :: MDX To Calculate Maximum Gap In Sales For A Product?

I have a fact table which lists the last 12 month historical sales of a product,country,month combination so the table structure is like:

<month, productID, countryID, (month-3 sales), (month-4 sales).........,(month-14 sales)>

I need to write an MDX query which will return a flag that indicates if a product has a gap of more than 2 consecutive months in terms of positive sales. So I calculate if there is a gap of 3 months. If yes, then return 1 else null. The calculation below is scoped at product level.

IIF(([month-3 sales]<=0 AND [month-4 sales]<=0 AND [month-5 sales]<=0)
OR  ([month-4 sales]<=0 AND [month-5 sales]<=0 AND [month-6 sales]<=0)
OR ([month-5 sales]<=0 AND [month-6 sales]<=0 AND [month-7 sales]<=0)
...............
OR ([month-12 sales]<=0 AND [month-13 sales]<=0 AND [month-14 sales]<=0)),1,NULL)

Unfortunately I cannot do this calculation at relational level as a product may have a gap of more than 2 months at country level but may not have this at a higher level in geography.

optimizing this as the performance is bad and other calculated measures are dependent on this. Based on this calculation, I can write a scope which sums up all products so that I get the count of products with a gap of more than 2 months in sales.

I have also tried CASE statement and NESTED IIFs but the performance is worse than the above.