Reporting Services :: Getting Total Of Group Values In SSRS

I am trying to build a report using SSRS.I need to retrieve a distinct value from my initial query and place this in the header or group row.The detail lines are hidden but may be expanded(shown).I then have another group row in which I require the sum of all distinct values from my previous group row.To explain pictorially I have the following:

-Scroll right to see the pink squares.Note that the total in the pink square is the sum of the individual var3 values distinct so 10 even when var3 =4 in euro currency.
-I have tried using sum(var5) but this will give the incorrect value as it sums all detail lines not just the distinct values.
-I have tried using another dataset but when referenced the grouping behaviour expected is non existent so where I expect 40 I get 80 i.e. sum disregarding values of var1 and var2 although these are the grouping variables.
-I need it to be dynamic so I am unable to use IIF(...).

If I could get var4 or var6 to be the totals I require I could work with that.I have also tried the following custom code:

Dim public unitLimit as Double
Public Function Getcpvalue(ByVal limit_amount1 AS Double) AS Double
unitLimit = unitLimit+ limit_amount1
return limit_amount1
End Function

[code]...