NtProtectVirtualMemory

[Segin]

Could someone clue me in to just what this means and why it is:
err:virtual:NtProtectVirtualMemory Unsupported on other process

A quick Google comes up that function is undocumented, so I don't have 
much info on it.

 From the wine source:

    if (!is_current_process( process ))
    {
        ERR("Unsupported on other process\n");
        return STATUS_ACCESS_DENIED;
    }

And that's self explanitory, but why is it "Unsupported on other process"?