Help with expression where field a in table a = field b in table b when tables linked by another field

[#1]

Hi

I have a Targets table comprinsing of the following type of information

UserId	Owner	Financial Week #	Sales Target Value
63	Jo Bloggs	1	500.00
50	Sam Smith	1	250.00
41	Jane Doe	1	600.00
63	Jo Bloggs	2	520.00
50	Sam Smith	2	100.00
41	Jane Doe	2	800.00

etc

I need to be able to caclulate total targets based on variables i.e:

Sum({$<[Financial Week #] = {'$(vMaxWeek)'},[Year]={'$(vMaxYear)'}>}[Sales Target Value])

This works at present as the Financial week # joins this table in the script to the calendar.

example:

It doesn't take the Owner into account though. I can't join the owner to the Users table (by UserId) without creating loops

Is there something I can add to the expression that means the sum is only calulated when the Owner seleted matches the Owner from the Targets table?

I've looked at creating a link table as a possible option, but can't see what I woudl use to make a key that wouldn't also create a loop..

Any ideas would be most appreciated, thanks in advance...

Heather

[#2]

Is anyone able to help with this i'm trying to write an expression that includes where Userid = UserID, but it only returns the correct results if you select both UserId and UserID  - and I just need it to sum the results where UserId in the target table matches the UserID of the Owner selected.

[#3]

This works:

Sum({$<UserId = {'138'},[Financial Week #] = {'$(vMaxWeek)'},Year={'$(vMaxYear)'}>}[Sales Target Value])

.... but not when I replace value 138 for field UserID