If you understand how the expression works, it's a simple and easily-fixed oops. You can skip to the end if you want the solution, but I think it would be helpful to review exactly what we're doing here rather than just cutting and pasting and calling it good.
Now, I'm not sure how much you understand or don't understand about what's going on in the expression, and even if you understand it, others who find this later may not, so let's start over from scratch. Let's go through the entire thought process that leads us to the expression I posted, though I guess I'll assume a decent knowledge of set analysis itself. Well, what we want is the behavior we'd get if we had something like this with nearly every field in it:
sum({<Customer=,Order=,Product=,...>} Sales)
All of those equals signs with no set after them say to ignore selections in that field, which is what we're after. But in a real application, with 100 fields, say, it's completely impractical to write them all out, and then maintain them as we add and remove fields from our data model. So what we'd like is some way for the system itself to list out all of our fields.
The system has a field called "$Field" where it tracks the name of every field in the data model. So let's say we did something like this:
concat($Field,',')
That would give us this string:
'Customer,Order,Product,...'
It's a string, though, so not directly useful. However, it's possible to evaluate and then insert a string into an expression by using dollar sign expansion, which is to say $(=...). Something like this:
sum($(='Sales'))
Gets turned into this:
sum(Sales)
Before being executed. The dollar sign expansion always comes first, with the result inserted literally into the expression. So then if we did this:
sum($(=concat($Field,',')) Sales)
We'd actually be processing this:
sum(Customer,Order,Product,... Sales)
That's not a legal expression, but at this point, we can just add the {<...>} and the equals signs to get a legal expression:
sum({<$(=concat($Field & '=',','))>} Sales)
Which the system would interpret like this:
sum({<Customer=,Order=,Product=,...>} Sales)
Perfect! So why aren't we done? Well, one reason is that hidden in the ... are Year= and Month=, so we're excluding every field. What we really want is every field EXCEPT for Year and Month. Well, every field but year and month is just a set analysis expression:
{1<$Field-={'Year','Month'}>}
So we need to insert that into our concatenation so that it skips those fields:
sum({<$(=concat({1<$Field-={'Year','Month'}>} $Field & '=',','))>} Sales)
The other reason we aren't done is that field names can contain whitespace. A field like [This is a Field] must be enclosed in brackets (or double quotes). However, the $Field field doesn't contain the brackets. So we have to string '[' and ']' around the field in our current expression. And that's how we end up with our final expression:
sum({<$(=concat({1<$Field-={'Year','Month'}>} '[' & $Field & ']=',','))>} Sales)
So now, with an understanding of exactly what that expression is doing, let's take a look at your expression:
max({<$(=concat({<$Field-={'Year={$(=min(Year))}','WeekType','CalendarType'}>} '[' & $Field & ']=',','))>} WeekEnd)
Now, the section of this where we do the $Field-={...} is where we're telling the system ONLY the names of fields that we do not want it to ignore. Year={$(=min(Year))} will in this case probably end up looking like Year={2012}, but the expression is going to interpret that as a field NAME, not as some selection you're making in the Year field. Since there's no such field name as "Year={2012}", I THINK the instruction will end up getting ignored, and the Year field will therefore be in the list of fields we ignore. You'd therefore get the maximum WeekEnd in the entire data set, not the maximum weekend in the minimum year, which is I believe the problem you're seeing.
So instead, we first just want to exclude the Year field from the concat(), which is to say to INCLUDE it in the list of fields we care about selections in.
max({<$(=concat({<$Field-={'Year','WeekType','CalendarType'}>} '[' & $Field & ']=',','))>} WeekEnd)
Then the part where you're selecting a specific year has to go into the outside bit of set analysis, not the inside bit, because the outside bit is where we're actually picking what WeekEnds we care about (instead of field names). So I think you want this:
max({<Year={$(=min(Year))}, $(=concat({<$Field-={'Year', 'WeekType', 'CalendarType'}>} '[' & $Field & ']=',','))>} WeekEnd)
