excel read using c++
You can use any of Microsoft's languages (VBA included) to open Microsoft applications. The exact interface (objects etc) depends on the version of the application that is being accessed. I recently wrote an article in Circuit Cellar that interfaced VB2005.net to MS Excel. It appeared in Issues 200 and 201 MArch and April 2007. It was related to using Modbus, so you may find the rest of the article distracting. Here are some related references that I used, just to get you started.
How to transfer data to an Excel Workbook by using Visual Basic .NET, Microsoft Article ID 306022
How to use MFC to automate Excel 2000 and Excel 2002 and obtain an array from a range in Excel 2000 and Excel 2002, Microsoft Article ID 186122
Microsoft Visual Basic 2005 Express help file: GetObject Function (Visual Basic)
How to automate Microsoft Excel from Visual Basic .NET, Microsoft Article ID 301982
An alternative may be to write your application from within Excel using VBA or Microsoft's latest languange VSTO.
-Aubrey Kagan