Since 2015 version of Solidworks, it is more than easy to create a custom property with "Total length" of structural members.
Version 2015 has a new custom property of the cut list called "Total length":
2015 What's New in SOLIDWORKS - QUANTITY and TOTAL LENGTH Properties
Therefore, using this macro:
it takes a few seconds to do it.
Follow these steps:
1. Create a note in the model and link it to $PRPWLD:"Total length". Make sure that your note now really show the sum of all structural members.
2. Run macro from the link, write "Length total" or your desired name in the input of the macro form textbox (assigning a button to this macro will make it easier to use)
3. Click "Link"
That's all !
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