[blairwillis]

What is the source of the drummer's click track?

If it is generated by something like a software sequencer or a hardware drum machine or synth, then the answer is simple. MIDI Clock Sync.

To try and sum it up, you will physically connect the source MIDI output to your Virus MIDI input, and set the Virus to External Clock sync mode in the Config menu.

When everything is hooked up properly, adjusting the tempo of the source device should result in the Virus tempo changing accordingly.

If this doesn't happen, then it may be necessary to set the source so that the MIDI clock signal is being sent to the appropriate MIDI port. For example, I use Ableton Live, and in the MIDI Preferences there are on/off settings for "sync" on each device output, and tend to be Off by default. Most hardware devices (synths and drum machines) tend to output MIDI clock On by default.