SSRS 2005 Subreport Parameter Challenges

Question

Good Morning,

I have written my main report that contains a field called MSDRG. I have also written a subreport, called MDDETAILS, that also contains the same field. In my main report, I've created a report parameter named MSDRG, available values non-queried. In my subreport, I've created a report parameter named MSDRG also. Settings are: available values from query dataset=MDDETAIL value field=MSDRG, default values from query dataset=MDDETAIL value field=MSDRG. In my main report, the properties for subreport are: Parameter Name MSDRG Parameter Value = =First(Fields!MSDRG.Value, "DataSet1").

The subreport runs fine by itself. However, when I run the main report, I receive an error stating: Warning 1 [rsErrorExecutingSubreport] An error occurred while executing the subreport ‘subreport1’: The report parameter 'MSDRG' is read-only and cannot be modified. m:\projects\cy09 ip\cy09iplos\losreports\FPSummary.rdl 0 0

I apologize if this is a basic question, but I'm new to SSRS coming from Crystal Reports. Thanks much for your help and guidance.

Sid