By "ramped" I assume you mean to sweep the frequency without stopping and restarting the counter. The following link should help you set up your operation to do this. There is an example program at the bottom of the page.
http://sine.ni.com/apps/we/niepd_web_display.DISPLAY_EPD4?p_guid=B9DF85FD9CD023DEE034080020E74861&p_node=DZ52328&p_submitted=N&p_rank=&p_answer=&p_source=External
David Staab, CLA
Staff Systems Engineer
National Instruments