For Local Report - Add Dropdown list outside of Report but use SelectedItem.value to return Report results

Simply, I hope... As described in title... A Clear VB.Net example would be greatly appreciated.

The dropdown list is provided from code below.
How do I pass this value to Query another table using SelectedItem, to provide data to to the ReportViewer - I tried researching how to, but cant figure this one outPLEASE HELP!

Populate Dropdown List:

Public Sub LoadProdCategory()

        Dim objConnPDC As SqlConnection
        Dim mySettingsPDC As New NameValueCollection
        mySettingsPDC = AppSettings
        Dim strConnPDC As String
        strConnPDC = mySettingsPDC("DIS_PHLINVENTORYConnectionString")
        objConnPDC = New SqlConnection(strConnPDC)
        objConnPDC.Open()

        Dim strPDC As String

        strPDC = "SELECT CategoryID, CategoryCode, CategoryDecode " & _
        "FROM ICDbS_ddl_Category " & _
        "Order by CategoryDecode ASC"

        Dim ObjCmdPDC As New SqlCommand(strPDC, objConnPDC)

        Dim ObjDRPDC As SqlDataReader
        ObjDRPDC = ObjCmdPDC.ExecuteReader()
        DropDownList1.DataTextField = "CategoryDeCode"
        DropDownList1.DataValueField = "CategoryCode"
        'Item_ProdCategory.SelectedValue = ("3")
        DropDownList1.DataSource = ObjDRPDC
        DropDownList1.DataBind()
        DropDownList1.Items.Insert(0, "")
        objConnPDC.Close()

    End Sub