Connecting V6 to Yamaha Soundbar

I have a V6 box, an LG TV and a Yamaha soundbar.

The remote has been set up to turn the LG on and off, but I want to control the volume of the Yamaha using the V6 remote.

I have tried the Volume Down/Clear combination, pressing 1999 and using the remote volume both up and down with a large number of tries but don't seem to get a response from the soundbar.

Is there an easier alternative method for pairing the remote to the Yamaha?

Thanks for any help