Adding two Ctrl + Shift select functions

I need to be able to check one check box in the lists then check another further down the list by pressing Ctrl + Shift so all the check boxes between the two checked check boxes are checked. I also then want to be able to go further down the list and select individual check boxes or repeat the process with the already checked check boxes remaining checked. This is for the player at wizps.com. Please do not press the navy blue add button because it will generate files which will take a very long time in to complete the process.