Open excel file with C/C++

For an automated test of electronic hardware I am developing a Windows program to superseed an old DOS based program. The tests are specified in a large number af Excel spreadsheets and for use of the DOS program, the cells in a spreadsheet is saved to disk by spreadsheetname and extension '.seq', then read into the DOS program an processed. The above mentioned Excel spreadsheets are maintained and developed over time and is therefore still usefull for the Windows program as well. The testequipment is connected to a PC direct througt relay's, through serial I/O and/or through network and are subject to change interface over time. Due to a lot of factors the overall design specification is set for no use of specialized tools like .NET, MFC, eg. the software must be written in pure c/c++ on standard Windows API. It is however alloved to use COM or ACTIVEX as long as interface to the components can be done through pure c/c++. So far the software written is covering MMI ( man machine interface ) with a number of nested Dialogs and a number of threads all initiated on program start. The threads is set to execute various functionalities, like file I/O, test sequence, seriel I/O and so on. The development system is Microsoft Visual Studio 6.0 Enterprise Edition and I use pure C/C++ with precompiled header. Some of the project files are written in C, so whatever solution You may end up with, it must be able to link accordingly. What I need now is a shortcut, so I directly can read data in a spreadsheet into my Windows program, this is the specific