I think you'll need a fair stroke of luck to get a useful pointer in this forum -- we ponder how to get things into Excel, not out.

Excel is just exceptionally convenient for applications like yours because it has a built-in gridded interface and a very powerful set of native functions. You'll have to duplicate some portion of that functionality if you abandon Excel, and whatever you do, it will be less familiar interface to the 10 zillion people that use Excel.

Maybe Google Docs is an alternative, but I have no idea how cross-platformy it is.