If you are able to write .Net you could use a PerformanceCounter to get the free space on a specific machine and drive?
PerformanceCounter PerfCnt_Disk = new PerformanceCounter("LogicalDisk", "Free Megabytes", [drive letter as in "C:"], [server name]);
float val = PerfCnt_Disk.NextValue();
From there you could simply write the values to a CSV file.
..Or if you're not a coder you could buy something off the shelf like this