increment user variable

Hello,
I am trying to increment a user variable every thermo output.
Some background, I am trying to get a soil bed to a certain void ratio. I am doing this by stepping 5000 and then checking what my void ratio is. If it is my tolerance, I continue the simulation. If not, I step another 5000 and check again.
What I would like to have though is a continuous simulation time in my thermo output. I was doing this using

variable sim_time equal dt*elapsed

but every time I would reuse the "run 5000" command, elapsed. I then tried the following

variable sim_time equal 0.0 # At the start of my code

variable old_time equal ${sim_time}
variable sim_time equal v_old_time+5000*dt

This set sim_time to 5000*dt.

Does anyone know of a way to get a continuous simulation time while using multiple run commands?

Thank you!