Here's a snippet from FiberOptics (I wrote one, then he wrote it better ;P)
tried //echo -a $dirsize(c:\temp) : $dirsize(c:\temp,b) : $dirsize(c:\temp,3)
: :
mIRC 6.16 on Microsoft Windows 2000 [Version 5.00.2195]
$com(%b).result was returning $null for all folders attempted on