How to get reference local position of axis in HAL?

I need to connect classic ladder input variable that will corresponds reference position of Z coordinate in G54. What variable can I use?
I want to connect this variable to classiclader and to block manual jog lover than Z=0 in G54 coordinate system.
Z axis minimum value always change and I don't want to damage table.
 

I've fount already.
I should use halui.axis.L.pos-relative