How to get WorldVariable startingValue in script?

I'm modifying your NGUI World Variable Listener script to target a slider value instead of a text component.

All works great except that I can't seem to get the variable's startingValue, or intMaxValue/floatManValue in order to normalise 

I'd want to do something along the lines of:

InGameWorldVariable _variable = WorldVariableTracker.GetWorldVariable(variableName);

int _maxValueInt = _variable.startingValue;

_slider.value = newValue / _maxValueInt;

but only the WorldVariable class seems to be able to access the startingValue property.

Is there a way of getting it without hard-coding it in the listener?

Also, does the listener have a reference to the variable itself? (i.e. is the first line of my pseudocode really necessary? or to put it another way why does your WorldVariableListner example class need: public string variableName = ""; If it's hooked up to receive new values, why does it not know the variable that this value belongs to? 

Thanks