How can I pass multi valued parameter to a subreport

Hi I have a main report having a report parameter @offices.

This parameter is populated from separate dataset and contains list of multiple offices.

Now I need to pass this multi valued parameter to a sub report contained in the main report. I have tried using below approaches while passing parameter value in Subreport properties->Parameters-

1. Join(Parameters!Offices.Value, ",") 

2. Split(Join(Parameters!Offices.Value, ",") , ",")

But nothing worked. Every time the first value of the ofiices list is passed to the subreport.

Please suggest.

Thanks.