double jump

Whats the best way to make a character double jump using the platform movement object extension, i tried my own way but it didnt work, any ideas?

Okay, Id use flags:

Object is standing on ground ---> Set internal flag 0 of PLAYER off


Upon pressing Shift (or w/e the jump button is)
+
Object isn't standing on the ground
+
Internal flag 0 of PLAYER is off --------> JUMP and set internal flag 0 of PLAYER on

This is an example made for Slink over at TDC by "Netninja"... whoever that is :O

Download link http://upload2.net/page/download/ZHfHyk4PdhOK6H9/double+jump.zip.html

(just keep scrolling down to the "download here" link...rubbish site)

Thank you very much!