You need to specify the classpath when you run the program too. Compiling doesn't link the library into your code as happens in C and many other languages; in Java linking happens at runtime.
Probably -cp .;C:\Users\chuser10\Desktop\Excel\src\excel\lib\poi-3.10-FINAL.jar will be what you need. The '.' at the beginning means the current directory, which is where the class files that constitute your program are rooted. The ';' is just a separator.