Start print at user defined Z height

[paboman]

Is it possible to start a print at a certain Z height defined by user without modifying the Gcode?
Lets say I have printed 500 mm in one printer an want to continue the job on another one starting from 500.2 mm

[dc42]

Only if you can work out the offset within the file at which the print starts the layer at 500.2mm.