Serial RS232 directly to a USB DAQ?

Hello,

I have a question regarding serial communication: is it possible to directly hook a device via RS232 serial to digital pins of a USB-6211 DAQ? (Or maybe even a USB-6008?)

If so, where should I wire the pins to?

If not, could you recommend me a not too expensive, yet functional RS232 to USB adapter which could work fine? (I am planning to interface a Datex capnometer or a Fresenius Pilot C infusion pump first, however if I could find a relatively well-priced multi-port adapter I would go on with both. BTW, can I include more NI-VISA queries in parallel in LabVIEW?) 

Thanks