Change the value of a pre-existing user message. Use rfg.AddUserMessage to create them.
Arguments:
- Handle (int)
The handle of the user message you want to edit. This is returned by rfg.AddUserMessage when you create a user message.
- NewText (String)
The new text to be displayed for the user message.
Returns:
- Handle (int)
The handle of the user message you've edited. This shouldn't be different from the one you entered.