Cast From String 'OPEN' To Type 'Double' Is Not Valid.

Hi.. Please help me resolve this error "Cast from string 'OPEN' to type 'Double' is not valid.". Error here If CallStatus = 10 Then ....
Code:
Public Sub UpdateCallStatus()
        Dim CALLID, RequestorID, CommentsFromITD, MessageFromITD, MessageToITD, CallStatus, strSQL As String
        CALLID = Request.QueryString("CallID")
        RequestorID = Session("USER_ID")
        CommentsFromITD = lblcomments.Text
        MessageFromITD = lblmessage.Text
        MessageToITD = txt_desc.Text
        CallStatus = Trim(Request.Form(ddl_callstatus.UniqueID))

        Dim ObjCmd As SqlCommand
        Dim ObjDR As SqlDataReader

        Try
            If CallStatus = 10 Then
                strSQL = "UPDATE CALLS  SET STATUS_ID=" & CallStatus & " WHERE CALL_ID=  " & CALLID & ""
                ObjCmd = New SqlCommand(strSQL, ObjConn)
                ObjConn.Open()
                ObjDR = ObjCmd.ExecuteScalar()
                gbVariables.insertuserevents(CALLID, RequestorID, "Call Closed")
                Response.Redirect("UserCallClosed.aspx")
                ObjConn.Close()
            Else
                strSQL = "UPDATE CALLS  SET STATUS_ID=" & CallStatus & " WHERE CALL_ID=  " & CALLID & ""
                ObjCmd = New SqlCommand(strSQL, ObjConn)
                ObjConn.Open()
                ObjDR = ObjCmd.ExecuteScalar()
                ObjConn.Close()

                strSQL = "SELECT STATUS_LABEL  FROM STATUS WHERE STATUS_ID = " & CallStatus & ""
                ObjCmd = New SqlCommand(strSQL, ObjConn)
                ObjConn.Open()
                ObjDR = ObjCmd.ExecuteScalar()
                ObjConn.Close()

                gbVariables.insertuserevents(CALLID, RequestorID, CallStatus)
                CallStatus = ""
            End If
        Catch ex As Exception
            lblmsg.Text = ex.Message.ToString
        End Try
    End Sub
Thanks...