[maxmsp] newbie - compiling a C program into a max external

Hi, hope someone can help me. 

I have no experience writing Max externals but am using an external for which I need to make a very small change (adding one extra 'if' statement to 28 pages of code!)

I have made the changes to the source code file (it is written in C)

All I want to do now is to convert this C source code into an external that I can use in Max/MSP.

I don't have Codewarrior or XCode running on my machine and as I am using a university computer, it is awkward to install any new programs.

Could anyone offer me any advice?

Thanks very much!

Anna