What version of Excel? VBA changed a bit between some of the versions.

Any chance you can attach a quick sample spreadsheet?

I've got a ton of experience with VBA in Access, but almost none in Excel, but it can't be too different. Are you passing the listbox byVal or byRef? If you haven't specified, it defaults to byRef (which is what I believe you want).

Is the little attached sample what you are trying to accomplish?