That would not be too difficult but it might be a bit misleading. The format string is resolved at the time of starting the recording. Doing the above would resolve it at a wrong time and show the wrong result. I suppose I could make it a "Validate" button and pop up a messagebox with the result instead of updating the label, making it clear that the result is just a sample and the actual file name may be different.

BTW, another thing I was considering was having an option to use the start or the end time of the recording for the file name generation. That is a bit trickier but not insurmountable.

That could work too but aesthetically there is not enough room for two buttons. So it's either "Validate" or "Clear", take your pick.