Diagram Protection will be damaged by Group Action ???

Hi,

I have draw a simple square shape. then I use protection function to luck
the "High" of this.
It works fine, since I can't change the shape's hight now.

but if I group this shap with other shapes. there is the problem !
when the group have been resized, the protection function is not working now.
The squire's Hight will increase with the Group.

why ?

how to avoid this ?

any ideals ?

thanks