Barney smiled against Billy's lips, returning the kiss.
He needed to know what Robin was doing. Suddenly worried that she might be doing something he wanted to see, he reached out the hand not cupping Billy's face and groped for her. When his fingers brushed off her arm he gripped it, tugging her forward. He wanted her where he could see her. He moved her to somewhere in his eyeline, but where Billy couldn't see and get freaked out.
He winked at her, bringing his hand to rest on Billy's knee as he deepened the kiss, the hand on Billy's cheek sliding back to cup his head.