Help on Set Analysis syntax on bringing in all values

[#1]

First let me say I'm extremely new to Qlikview (a week). Great tool!! Anyway,
I'm trying to create a chart that shows me Products (Dimension) by the following Expressions, Sales, ProductTheme, Sales Channel, MonthandYear and finally %Change (% changes in MonthandYear).

However, I'm guessing because I can have several Products in the Channels and MonthandYear, I get very little data (mostly dashes). I'm guessing because I do get some dates, assuming only one Product was sold in that MonthandYear.

And, after all that, I'm really struggling with the syntax for the %Change. Here are a few of the things I've tried;

//Sum ({$<Calendarwrittenmonthandyear>]} SalesAmount)/CalendarWrittenMonthAndYear-1]}SalesAmount)-1]}

//(sum({$<CalendarWrittenYear={$(=max(CalendarWrittenYear))}>} SalesAmount)-sum({$<CalendarWrittenYear={$(=max(CalendarWrittenYear)-1)}>} SalesAmount))/sum({$<CalendarWrittenYear={$(=max(CalendarWrittenYear)-1)}>} SalesAmount)

//sum({$<CalendarWrittenmonthandYear-1>={$(max(CalendarWrittenMonthandYear))}>} SalesAmount) /sum({$<CalendarWrittenMonthandYear={$(=max(CalendarWrittenMonthandYear>}SalesAmount)-1

//(sum({$<CalendarWrittenMonthandYear={$(=CalendarWrittenMonthandYear)-1>SalesAmount)/sum({$<CalendarWrittenMonthandYear>} SalesAmount)-1

//sum({$<CalendarWrittenMonthandYear={(CalendarWrittenMonthandYear-1/CalendarWrittenMonthandYear>)-1> SalesAmount)

sum({[Variable2]}SalesAmount)

Where Variable2 = (CalendarWrittenMonthAndYear-1/CalendarWrittenMonthAndYear)-1

Can anyone Please Help!!

And my apologies in advance if I'm wasting anyone's time for such a simple question.

Thanks

[sebastiandperei]

You should send a sample