How to build a multi-select dropdownlist?

I have an SSRS report that lists all my open orders.  I want to make a change where I can provide a dropdownlist or some equivalent where I can select one or more orders.  It would even be better if I could also select ALL orders.  Is this possible? Does anyone have  an example?  I probably have to create a new dataset to populate my dropdownlist parameter.  Something like:

SELECT OrderID

FROM OrderHeader

WHERE OrderStatus = 1 (Open orders)

ORDER BY OrderID

But I would need a WHERE clause in my main query something like:

WHERE OrderID IN @OrderID (multi-select parameter)

I need some help building this parameter and also the dropdownlist parameter.  I wasn't sure if there is something built-in to SSRS that already does this.  Can anyone help?