If you are using LV version 7 there are a few express vi's that might help. Try using the Simulate Signals and the Simulate Arbitrary Signals express vi's. These vi's will allow you to configure the signal to be a sine wave, square wave, etc. and will generate these points for you to use. Basically simulating a daq device like you are asking. Hope this helps.
BJD1613
Lead Test Tools Development Engineer
Philips Respironics
Certified LV Architect / Instructor