I don't know of an easy way for a single variable, M-Register, or output. There are parameters to reset all.
What you could do is write in the ladder when address 70017 turns on turn on a general purpose input. 70017 is a first pass bit. It turns on once the ladder has gone through a scan upon boot-up. The rung would need to be broken with a general purpose output as a handshake.
STR #70017
OR #0xxxx
AND-NOT #1xxxx
OUT #0XXXX
Both 0xxxx addresses are the same.
In your job you can look at the general purpose input's status. If it is on reset this and turn on the output to break the seal. If it is not do this.
This may need to be massaged a little bit. Maybe more conditions added such as PLAY or OPERATING. I don't know how your outputs are configured. Initialize on boot-up or last state.
