Excel Validation List, using a different worksheet for source?

Has anyone figured out a good way to "trick" excel so that you can set up a validation list on a seperate worksheet? I can't put the data on main worksheet, as the user needs to save it as .csv so it can be imported into another program. The import routine wouldn't know what to do with the extra data, yet the import will fail if certain data doesn't match the values it is expecting.

any hints would be appreciated!

Thanks,

Tamara