after bugging around with the tool “passchg” (from  http://ctrl-alt-del.com.au/CAD_TSUtils.htm) to change the password on a remote computer i finally found a shortcut to send ctrl + alt + delete …

just hit “ctrl + alt + end” …

as this will not work in a nested rdp-session i still have to use the tool there .. but for 90 % of my sessions this will work for me …