[openbox] Pressing keys assigned in openbox opens too many windows in Ubuntu

[sc.marko.toivanen at gmail.com]

Is there any way to configure key bindings in openbox so holding down a 
key combination would not open more than one instance of a program? E.g. 
when I have configured to use Shift + Alt + T keys to open a terminal 
window, if holding down the keys too long time, there will be a lot of 
terminal windows open. It should open only one terminal window and if 
pressing Shift + Alt + T again, then it would open a second etc.