Status Bar - or a script

I would like to compute the average file size for a directory. I have tried using the status bar code:

{cp+V=tba/tf}

but this does not work. Specifically, it produces a "0". My thought is that {cp} is designed only for percentages, and cannot handle any number that is not from 0..1.

So, is there any convenient way to display in a lister, the average file size for a folder?

Thanks in advance,
Kevin

Not in the status bar, but a script could calculate it and show it in either a popup message box or as a column shown next to each folder.