By manually, do you mean from the front panel? If you really mean programtically, then use ag33xxx - Config Waveform like I said inside a loop. A shift register would be initialized to your starting value. Inside the while loop, wire the shift register to the frequency input of the ag33xxx - Config Waveform function. Also inside the loop, increment the shift register by another control that you specify a value for. Add another control for a stop value and terminate the while loop when the current value of the shift register is equal to/greater than the stop value. I've attached a picture that I did just a couple of days ago for an almost identical question (just a different instrument). The picture has a constant for the start and stop value so if you want to use different values at times, replace them with controls.
If you want an uneven step value, you can place an array of values outside a for loop and auto-index the array.
