You need to split to two text boxes with the same expression. You will need to add some code to move one or both of the lines vertically based on the scale so as to adjust the space between the two lines as well.
You want to include the marker’s time there and compare to current time. While you should be able to do it by checking if marker time equals current time and running the function if so, might be more foolproof to check whether current time is equal or more than marker time and current time minus one frame is less than, and if both conditions are true then run function.
You can use this on the individual walls (on an adjustment layer matching the size of the comp, for instance) and get something quite close to that transform.