Read the help for LabVIEW.
It is written that
"The multicolumn listbox includes columns where you can add more information for each option, such as the size of the option and the date it was created. You can set the number of columns and create headers for each column."
I think this means that actually you have an ordinary listbox but with some additional info. And columns are used only for some extra info such as units of measurements, etc. The rows are the options of this list box, but not the cells.
May be I'm not right but I think that the word Listbox means the one demension.
Oleg Chutko.