Here is my solution. Worked with script, which was ran by third party program with no WScript declared and no import allowed.
Function MySleep(milliseconds)
set WScriptShell = CreateObject("WScript.Shell")
WScriptShell.Run "Sleep -m " & milliseconds, 0, true
end Function
Update
Looks like Microsoft removed Sleep.exe from win 8, so this doesn't work in win 8 unless you put Sleep.exe in folder defined in %path%.