Can i force a grape vine to create a new branch?

Hi,

I am training a grape vine onto a trellis. Is there a way that I can "encourage" the grape to create side branches?

Oops. Didn't finish my post.

Consider that the grape is planted at the base of post (P). I currently have a main branch going up the post. I want to get branches on each side of the post at lines A, B, C. Is there anything I can do to encourage branching or am I subject to nature and the plant?

Not sure on grapes. With blackberries you would have 3 canes coming up. Cut one 4" above a, another 4" above b and another 4" above c. Except b is not there. It's a two wire system.

Btw, why 3 wires instead of one or two? I'm looking to plant grapes this winter.

We already have multiple branches on the vine. I would like to encourage more in a more deterministic manner.

The diagram is not exact. But we have multiple lines and the purpose is to shade a brick wall that picks up a ridiculous amount of heat in the summer. The total trellis is almost 6' tall.