Option to have "none" or "any" of the fields required

Depending on the transaction, I may only need a class, or account, or description. I never always need one particular field filled out. Right now I have the description set as required because this is the most likely to get me the information I need, but it feels like a burden to the client if all I really need is for them to choose a class. At the same time, I'd like for them to be able to choose what field they fill out, so that they can add a description if they're not sure what other options to choose. So either not having to choose a specific field to be required, or filling out at least one field meeting the requirement would be great!