pass value to sub report

hi ,
I need to pass multi selectes value to my sub report. to do so , i have done like the following,
=Parameters!ReportServer.Value & "/ResourceCost&rcarameters=false&rc:zoom=100&rc:Toolbar=true&BU=" & JOIN(parameter!BU.label)

Bu is the multi select value and need to pass ot to the sub report dataset mdx query.

sub report mdx:
SET [FilteredBUSet] AS descendants({strtoset(@.BU)},[Account—BillingCodeDsc].[Billing Code Description],leaves) .
How can i achieve this task. cant find a way. pls help me.
The problem is like this guys. once we click the link in the main report , it should go to the another report. multi selected values in the main report should pass to another report. need to access those coming params to access in the mdx query in the navigated report. can use like following in the navigation tab -> jump to url and can use the following.

=Parameters!ReportServer.Value & "/ResourceCost&rcarameters=false&rc:zoom=100&rc:Toolbar=true&Year="
& Fields!Year.Value & "&Quarter="
& Fields!Quarter.Value & "&InScope="
& InScope("Months") & "&Month=" & Fields!Month.Value & "&Sample=" & (Fields!Business_Unit.Value)

this business value is the multivalue. it may contain lot params like that. this also have some problem. and also if we have lot of params to pass to other report then cant use query string coz of the limitation of the query string. so can some one say how to pass param values to another report in good manner?
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I used this to pass multivalue parameters to a subreport

example

=Split(Join(Parameters!GDC1.Value,", "),", ")

=Join(Parameters! <ParameterName> .Value,", ")

An expression that concatenates all the values in the array of a multivalued parameter of type String into one string.

=Split("Value1, Value2, Value3",",")

Takes a string and creates an array of objects that can be used to pass to a subreport or drillthrough report expecting a multivalue parameter.

http://msdn2.microsoft.com/en-us/library/aa337292.aspx

hope this helps