Problem solved better
OK, I really hope the original poster solved his problem since now 5 years has passed, but I thought I'd post this to help the others out there who might have the same problem.
There is a quick and easy way to do this actually. Set the voltage source up as a PWL, with one period's worth of data. A PWL string will appear next to the voltage source in the GUI - e.g. for a signal stepping between 0, 1 and 2V every second the string would say PWL(0 0 0.99 0 1 1 1.99 1 2 2 2.99 2 3 0). Right click on this string and stick in a "repeat forever" and a "endrepeat", so it looks like this: PWL(repeat forever 0 0 0.99 0 1 1 1.99 1 2 2 2.99 2 3 0 endrepeat). Done!
If you want the signal to repeat only 5 times, for instance, you would put "repeat for 5" instead of "repeat forever".