What are my options on multiple users accessing and editing a MS Excel 2010 workbook on a network?

I am not an expert but I have self taught myself some VBA.

I work in a paper based office and I am currently making a large MS Excel workbook, with 5 sheets, to use as a control point for the paper files. This means all the data also has a diary date attached and the data is edited regularly (such as when work is complete/diary to check the file needs changing etc).

I have used VBA and an auto_close macro so the workbook data re-orders itself across all sheets via the date it needs to be worked and then saves, so that the next person in the document can work the next task in date order - kind of like a diary system. I'm also considering (probably ambitiously)  if I can use VBA to link up the diary dates on the workbook with outlook to save time.

I want to role this out to an office of 20 and have considered sharing the document for "collaboration" but this seems like a gateway to hell when I have read up on it. I have also considered SharePoint, but trying to convince my IT department to shell are for this is unlikely. I have also considered MS Access but I think I would have the same issue. An Intranet option seems the most likely work-around from what my un-IT-educated internet trawling brings up.

Does anyone have any suggestions so that each user can edit the document without others being locked in it whilst the file retains the macro function?

Thank-you for any advice.