You should take a look at Win32::Process::Info. It uses the WMI interface (under 2K/XP) to retrieve just about everything retreivable. Whether the the particular piece of information you are after is amongst them I cannot confirm as A) I use NT which does have the WMI interface B) CPAN is currently down (or at least inaccessible from my machine).

The interface is simplicity itself.

my $pi = Win32::Process::Info->new( undef, 'WMI' ); 
my @procs = $pi->GetProcInfo();
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@procs now contains a hash for every process in the system contina a key for (just about) every conceivable piece of information available from the system. If the module has a flaw it is that you cannot ask for the information for just a given process, but the overhead (on my NT box at least) seems minimal.

I think that you will find this easier than querying the information from the WMI yourself using OLE, if for no other reason than the information you need for that seems to be hidden away such that it is only acessible if you know exactly what you are looking for. With the module, the author has done all that searching for you :)