How to use a property as a reference paramter with calculation in getter, setter

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C++

reference

I have a function that needs a reference as a parameter like
Editfield( BYTE& value, .... )
works OK as long I use direct access in getter /setter with BYTE& as return like

__declspec (property (put = _SetPropsText, get = _GetPropsText)) BYTE propsText;
void _SetPropsText(BYTE val) { ((BYTE*)&props_new)[1] = val; }
BYTE& _GetPropsText() { return ((BYTE*)&props_new)[1]; };

But at all I don´t understand the function of getter and setter because removing the & in the getter fails:

__declspec (property (put = _SetPropsText, get = _GetPropsText)) BYTE propsText;
void _SetPropsText(BYTE val) { ((BYTE*)&props_new)[1] = val; }
BYTE _GetPropsText() { return ((BYTE*)&props_new)[1]; };

does NOT work or function calls!
It is OK using things like:

propsText= 12; 

but never works as a referce in a call as parameter

The problem I cannot resolve is, when I use calculation in my getter/setter like:

__declspec (property (put = _SetPropsTextSize, get = _GetPropsTextSize)) float propsTextSize;
void _SetPropsTextSize(const float val) { ((BYTE*)&props_new)[2] = (BYTE)(val*10); }
float _GetPropsTextSize() const { return ((float)((BYTE*)&props_new)[2]) / 10; };

and then call

EditFloat( float& , ...)
EditFloat( propsTextSize, ...)

any idea to overcome this?

What I have tried:

I have no idea to overcome this, imho it works in C# but not in C++?
A temp var does not solve it becuase the setter is not called when the temp var will be changed

when ever there is a "=" teh Setter is called, but when there is a & the getter is called
(checked with debug)