How to get this age of month sales expression?

[#1]

How to get this age of month sales expression? Someone can show about my problem from this picture.

I want to get AGE_OF_MONTH Expression. For example :

if YEAR = 2008 and PRODUCT = ABC SUSU. It's min(YEAR), so the result is Num(Month(END_DATE)) - Num(Month(START_DATE)) = 9.

if YEAR = 2009 and PRODUCT = ABC SUSU, YEAR -1 (Last Year / 2008) they found a START_DATE, the result is 12.

If YEAR = 2012 and PRODUCT = ABC SUSU, is the Max YEAR, so the result is Num(Month(END_DATE)) = 4.

but if YEAR = 2012 and PRODUCT = CACA, it's not found last year. So the result is Num(Month(END_DATE)) - Num(Month(START_DATE)) = 2.

Can someone to help me to make this expression?

Thanks

[lironbaram]

hi

attach is an example

hope it helps you

i got diffrent result for the first year  of producrs because if you do for example

num(month(END_DATE))-NUM(monnt(START_DTAE)) for abc susu in 2008 you get 8 and not 9

[#3 · Accepted solution]

This is the right code :

if(YEAR=min(TOTAL <PRODUCT> YEAR),num(month(END_DATE))-num(month(START_DATE)) + 1,

    if(YEAR=max(TOTAL <PRODUCT> YEAR),num(month(END_DATE)),12))

Thanks.