To set the current directory on the FTP server, you call InetDir, and specify a "SET" operation.

The first arg is the name of the directory. This can be qualified relative to the current directory. For example, assume your current directory is "Dir1". There is a directory named Dir2 inside of Dir1. Inside of Dir2 is another directory named Dir3. You can pass an arg of "Dir2/Dir3" to set the current directory to Dir3.

/* Set the current directory to "Dir3" (inside of Dir1/Dir2). */
err = InetDir("Dir2/Dir3", "SET")
To descend out of a directory, into its parent directory, you can specify "../" as the name.
/* Set the current directory back to "Dir1" (ie, descend out of
 * both Dir3 and Dir2)
 */
err = InetDir("../../", "SET")
Note: You can omit the "SET" arg since that is the default operation.