Terry, if you want to record the data at an interval of the rate of the data acquisition, then you already have most of what you need.
Just divide the acquisition time down, so that you can determine the time between samples. Then, figure out the interval in number of samples, and when you reach that interval (use the divide/remainder function to tell) just set a case inside of your acquisition loop to true, and copy that data into another array, and save that whenever (or immediately.)