First you create your datasets like Products, ProductType, ProductName. Then in the ProductType dataset you put a parameter in the SQL for your ProductID. and then the same for ProductName. Then for each report parameter you set the parameter to use the appropriate dataset as it's source. This will automatically cause the parameter lists to "cascade"
Attached is an example using the AdventureWorks database (available on codeplex).
Jack Corbett
Consultant - Straight Path Solutions
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