Attribute of a cabinet-setting tiles

Hello

When inserting a trunking into the 2D cabinet layout of an electrical diagram, its length can be selected and easily changed. I would like this value to be automatically displayed on the chute symbol but I can't find the corresponding attribute... I tried to draw a dimension directly on the symbol but it keeps the same value regardless of the length of the chute inserted on the 2D cabinet-making folio ....

Another idea to propose to me or possibly the attribute corresponding to the value I want to display? 

Thanks in advance