The PCI-6024E can generate a signal at a rate of 10kS/s using DMA and at 1kS/s using interrupts(system dependent). If you are using interrupts,you will not be able to output a signal with a frequency greater than 500Hz.
If you are using LabVIEW, there is an example program called Continuous Generation.vi that uses DMA. Using this example, you can set the Update Rate to 10,000 and waveform that is output will have a frequency of 1kHz.