Yes, you can

I haven't done this with Chloe as she's not a serious barker, but I know that several folk on here have trained their dog to bark on command only.
Here goes:-
1) Trigger the barking (knock on the door, or table, or have a friend ring the doorbell...anything that you know will get Henry going). Whilst he is barking, click and immediately give hm a treat.
2) As he swallows the treat, make a shh gesture with your free hand, right in his face. He will look surprised. Click that expression, move your hand away, and treat.
3) Wait for the barking to start again (or trigger it). Click during a bark and treat. As he swallows, surprise him again with the shhhh cue, click and treat. Repeat the sequence several times.
4) As the shhhhh cue starts to work, you'll see him try to keep his mouth closed, after he's eaten the treat for barking. He wants to earn that next click and treat. Great!
5) NOW say Speak! and click the next bark. Follow with the shhhhh cue instead of the treat, and then click and treat for silence. You are teaching two cues. As he is learning the speak cue he may whine or yip. Click any sound at first, then just "woof".
6) To make the new cues very permanet, keep clicker and treats handy and reinforce "speak" and "shhh" at least once or twice any time he barks for a few days.
There you go...problem sorted...

As I said, I haven't tried this, but it sounds good to me

Pretty hard work though
