How to build a program that can read the content of a very simple MS Excel file?

["Huge Mountain" <educatenter gmail com>]

Hello everyone.
I'm trying to build a program to read the content of a Microsoft Excel file, just read a very simple Excel file (a file with text in cell A1, A2,..., don't care about formula, chart,...). I simply want to read the content of cell A1.  With that, I can get the binary format of MS Excel file more clearly.
Ex:if cell A1 have the content: "text message", my program can show "text message" as result.
Could someone tell me how to do that, or where to find the references? I downloaded source, file "
gnumeric-1.6.3.tar.gz" from http://www.gnome.org/projects/gnumeric/, but I don't know how to use, which to compile. I'm stray  with >1000 files (some file I don't know how to open).
Please help me!
Thank in advance!

PS:  I explored a simple MS Excel file (with "abc" in cell A1, this file was saved by MS Excel 2000). This file have 3 stream: SummaryInfomation stream, DocumentSummaryInfomation stream and 
Workbook stream. The only stream I care is Workbook stream, started from byte 512 to byte (512+4096) (this stream has the 4096 bytes length). So, where are bytes which contain the "abc" string of cell A1 in this 4096 bytes? 
Please help me!