Multi-selection of second input control's output in a cascaded parameter report.

I have a cascaded paramter report with 2 multi-select query input control which works fine. When i select a value in first dropdown, the second dropdown's values change accordingly and the first value comes as selected. I wanted to have a functionality such as if i select a value in first dropdown, the second dropdown's whole output will come out as selected and further we can deselect/select as per our use. How do i achieve that? Do i have to do something in control and resources? Please, Help me out here.

Thanks.