Check MSDN

search in MSDN and you will find with "PE Format" you can find 2 Technical Article:
1. Peering Inside the PE: A Tour of the Win32 Portable Executable File Format by Matt Pietrek March 1994
2. YAHU, or Yet Another Header Utility by Ruediger R. Asche
Microsoft Developer Network Technology Group, January 10, 1995
you can also visit http://www.magma.ca/~wjr/ for a PEview Tool to peek into the Portable Executable File inside deeply.

So, at far as I know, you can intercept the import table to "replace", say, a Kernel32.dll function, BUT, I don't think you can replace a function for there is no information about.




:rolleyes: