I'm having the darndest time trying to input data into the fourth column of my combobox. I think i am missing some code somewhere, but i don't know what, nor where exactly.

Could somebody view the source of my file and possibly tell me what i need to add/modify/or what format to use in order to input data into the fourth column (upon selection of an item in the third column)

http://www.freewebs.com/sackz/test.html