how can I simulate a vco for clocking flip flop use for 3 phase inverter

Thank you for the Answer you gave on'index exceeded'. please, am simulating a three phase inverter. I need a clocking signal from a vco that will clock 3 J-K flip flops for driving the gates of the inverter, but I am finding it difficult to simulate. This is the fifth day. I need your help. Thank you very much.