Write and read to a file in C:\

I want a mql4 script which creates a file at "C:\data.csv", writes a string to the file, reads the string back out of the file. Then writes a new string over the top of the old one and reads that out.

To do this I want the following functions

int errorcode = WriteFile() (this function should create the file if it does not exist, if it does exist writes the new string over the old)

int errorcode = ReadFile()

The string can just be a global variable

The difficulty here is file operations outside the mt4 sandbox.