Stepping/reaching out of bounds during a throw-in

[Lotto]

I do most girls JV here in New York, under NCAA rules. Here's a situation that came up the other night and how I handled it. I looked at the rulebook when I got home, but I couldn't find the answer.

A1 is taking the ball out of bounds. B1, who is guarding A1, steps out of bounds. I blow my whistle and tell B1 that if she does it again, it's a technical foul for delay of game. (Should I have gone to the table and informed them at this point? I didn''t....) At the beginning of the 3rd quarter, I pulled both team captains aside and told them that since I had already issued a warning for this, the next violation by either team would be a technical foul. I also told them to tell the rest of their teammates. Late in the 4th quarter, with 8 seconds left in the game, this happened again. I blew the T. The coach said she hadn't been warned and I told her that I had warned the captains.

Did I handle it right? What's the mechanic for this sort of thing?

Thanks in advance,
-Ben