I am using Windows SharePoint Server 2007. In a custom list, if I have two columns. One has a list of Categories, and the second has a list of Products. So in my Categories Column its a Choice with CheckBoxes to allow for multiple selections. Lets take an example the categories are Cars, Trucks, and Motorcycles. In the Product Column it is also a choice and with CheckBoxes that allow multiple selections. For my example I have Mustang, Camaro, F-150, Sierra, Harley, Kawasaki. Is there any way to check whether a selection in the second one had its parent checked, IE I check Camaro, and F-150, is there anyway to check and see if Car, and truck was checked in my first column?
I think you can accomplish what you're trying to do with SPCascadeDropdowns in SPServices, if your goal is to enforce the relationships.
If, instead, you just want to check the situation once the user has made their choices, you can do that with some script of your own.
If you are using Choice columns, what you need is a lookup to another lookup which is not supported OOB in SharePoint. In SharePoint 2010 you could make use of the new managed metadata column type which supports hierarchical data, but that is not an option in 2007.