According to the Help file..
[quote]Set FORMAT !folder
Finds and applies a folder format by using the same rules as when the folder was initially loaded. This gives you the same folder format as going out of the current directory and back into it again.[/quote]
From observation, this is only true if a matching folder format exists. If there is no matching format, no change is made so the second sentence does not apply. In this situation I expected, and would prefer, that the default (!custom) format would be applied.