@FILESIZE

@FILESIZE[filename,b|k|m[,a]]:  Returns the size of a file, or "-1" if the 
file does not exist.  If the filename includes wildcards or an include 
list, returns the combined size of all matching files. 

The optional third argument a (allocated), if used, instructs @FILESIZE to 
return the amount of space allocated for the file(s) on the disk, rather 
than the amount of data in the file.  Network drives and compressed drives 
may not always report allocated sizes accurately, depending on the way the 
network or disk compression software is implemented.