Is there a way to get the location of the last FIT-file that is written to the disk, (using DBUS)?

I'm having the problem that I have a slow drift of my object from the chip. I try to solve it by executing a script every 10 exposures. I just keep the number of exposures in a file in /tmp directory. I execute the script for every file in my sequence. Every 10th file I execute a solve-slewtotarget sync on the last file that was written to the disk. Doing a new exposure for the platesolve operation would take too much time and would give me gaps in my timeseries. This way the object stays centered on the chip.

Basically, it's a very slow "autoguiding" on the frames that the main camera is taking.
I'm having everything figured out, except finding the location of the last written file.