Applications :: Adding Drop - Down Menu In Numbers

I am attempting to modify the given template CHECKING ACCOUNT REGISTER in Numbers. I have figured everything out except how to modify the "Category" column where a drop-down menu is given for several recurring items (Home/Gas/Food/etc.) that are to be entered in that column. I would like to find how to create such a column or to be able to modify the one provided in the template. The TRANSACTIONS table is linked to the ACCOUNT CATEGORIES table which is linked to the CHART. That is intact and working as it should, but I have been unable to alter the column CATEGORY so that the drop down items will be ones that I want to use. Having the drop-down menu insures proper itemization in the linked ACCOUNT CATEGORIES table where typos are avoided as a result. The PDF manual was of little help (to me anyway) in addressing this seemingly simple alteration.