Have you looked at sharing the Workbook?

TOOLS SHARE-WORKBOOK

This seems to be the route your asking about, but there are some limitations that are applied when it is converted to a shared book in relation to conditional formatting and macros. This is right out of the MS Excel help files on workbook sharing

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Share a workbook
Create a workbook you want to make available for multiuser editing, and enter any data you want to provide.
If you want to include any of the following features, add them now: merged cells, conditional formats, data validation, charts, pictures, objects including drawing objects, hyperlinks, scenarios, outlines, subtotals, data tables, PivotTable reports, workbook and worksheet protection, and macros. You can't make changes to these features after you share the workbook.

On the Tools menu, click Share Workbook, and then click the Editing tab.
Select the Allow changes by more than one user at the same time check box, and then click OK.
When prompted, save the workbook.
On the File menu, click Save As, and then save the workbook on a network location accessible to the intended users. Use a shared network folder, not a Web server.