Rasinc,
When you're using parameters with a command, you MUST create the parameter in the Command Editor, not in the report itself. The Command Editor cannot see the parameters that have been created for the report. However, when you create a parameter in the Command Editor, you can see it in the Field Explorer in the report after you save the command. This allows you to, if necessary, set all sorts of properties on the parameter that are not available when editing the parameter in the Command Editor.
-Dell