Sorry. I do realize the format wasn't your choice.
Excel is much more than a math program. Visio is more of a graphic display tool with added in data linking.
Unfortunately, your options are dwindling rather rapidly and your management needs to come to grips with reality...
1) there's no existing Visio solution that I've encountered. You may give David Parker a try. He does a lot with Visio and data management. I believe his website is
http://blog.bvisual.net/2) expedite purchasing the Excel add-in. Any chance of an evaluation copy?
3) understand that a custom code solution will require a lot of time
4) accept a different format...a progressive bar chart for each business sector could be very effective. Each sector is represented by a bar that is sub-divided projects. The total bar length represent total allocations, each sub represents project allocations. Would be simple and effective.
Probably not what you want to hear, but I think those are your choices.
Wapperdude