Problem description:

No code here. Since I'm at a lost for words.

I need help making it so that whenever an invalid command is typed into the command bar, I can give out a particularly string of text so that the user knows what to do.

Any help?
See the "desc setting (verb)" page in the DM Reference in Dream Maker.

Other than that, it would help to know what an "invalid command" is. If you're using your own parser or something, you'd have to check for a valid command and produce some output when no valid command is found.
TY for the speedy response.

However, the 'Desc setting(verb)' isn't quite what I'm looking to do.

Pretty much, I'm using the basic Byond Command Bar -- where you can type something and activate a verb. What I want it to do is similar to various MUDs Ive played.

Where if you put in an invalid command (which is something that's not a verb) it'll give you a message prompt like.

'that command is invalid. To see a list of valid commands type /commands'
In response to Meme01
Assuming you're talking about the Input element, which is at the bottom of a default skin interface, above the status bar, rather than the Client>Command menu item in Options & Messages:

Unless you override client/Command(), players aren't going to be typing invalid verbs. The start of command text is limited to the verbs that are available. <-- nonsense

If the arguments given to the verb are invalid, they'll see the usage text which is provided by the "desc" setting.
I was talking about the Input element, correct.

But hrm, I see what you mean about the desc setting. Is there a way to override it so that anything thing submitted into the input element that -isn't- a coded verb will release a specified text string to the output?

Pardon if this is a bit elementary, but I'm having trouble grasping it. I manipulated the 'Command' and 'Command_text' but it didn't work out as well as planned.
client/Command(command) // This'll be called if something invalid is entered into the input.
src << "The command [command] is not valid."

Most MUDs don't use verbs at all, but use client/Command() to parse the 'command' argument to handle things manually, but it's not required.