axis movement until sensor is reached

[PowerCube]

Hi everyone,

Does somebody have an elegant solution for the following:

I need a modified G31 that:

- if the state of the LED is true: moves the axis in the negative direction until the state of an LED changes from true to false
or
- if the state of the LED is false: moves the axis in the positive direction until the state of an LED changes from false to true.

[Battwell]

the homing function would be the same as this?
explain what axis and its reason?