Dropdown Lists in both Excel and Open Office

Question

I have an Excel workbook which works as a time sheet. Users select the project they worked on and how many hours they spent on it that week. The project can be selected from a dropdown list showing all projects currently active.

The dropdown list is a data validation list containing a formula which points to a hidden sheet which lists the projects.

This works on Excel but not Open Office. The dropdown list data validation feature in Open Office is for hard-coded lists only, not dynamic cell references. To do those, I have to choose 'cell range' in Open Office. But 'cell range' is not supported in Excel.

So either I have a working dropdown list in Excel, or in Open Office, but I can't find a way to make it work in both.

I'd prefer not to have to create an *.ods version as this would complicate things for our admin team.

Is there a cross-platform way to do this?

Kind regards,

Chris