Based on your previous posts, I assumed that you want to supply appropriate commands to an external frequency synthesizer.
If you want to implement a frequency synthesizer inside the FPGA, you may design a DDS which supports several Sine waves (search about how to generate a Sine wave digitally). Also you may use PLLs inside FPGA and try to program their parameters on the fly. I'm not sure how difficult it is to do the last.
P.S.: You cannot generate high frequency Sine waves inside FPGA, specifically if you target Cyclone-II.
