If you cant teach a reference position because of varying positions then i would use an offset to that point/position register it would look like the following:
L PR[X]mm/sec CNT Offset, PR[X]
DO[X]=ON
L PR[X]mm/sec FINE
The offset PR[X] will consist off an X,Y, or Z offset so maybe -70mm should get you about 90% the way there
Then you will continue to the move but w/o the offset PR[X]
Be sure to make it a CNT termination so that the robot swims right through that offset point. That's all i can think off w/o using POS REF