just found this out, some people may find useful
HEALTH WARNING - PLAYING WITH SETTINGS IN ENGINEERING MODE MAY DESTROY YOUR BLACKBERRY - YOU HAVE BEEN WARNED!
first you need to select ALT, then type in the letters ESCR
however the 9105 does not have an alt key and has a numeric keypad
so to select ALT, press the folowing keys:
you should now see an ALT flag in the top left
then single press the numeric key on the key pad which containts the following four letters in sequence:
enjoy! (or destroy! - whatever