Hi, could you please give some more details about what you want to get?
If you want to have Analog Output from Mulitple Channle, you can refer to this sample.
http://digital.ni.com/public.nsf/allkb/44F1067EA1893DF586256F4D001A1E14
If you look in the NI Example Finder, search for analog and scroll down to the Gen Mult Volt Update - SW Timed.vi as an example. Alternatively, you could do the DAC updates based on a hardware timer, then then use the software timer to calculate your square wave frequency.
