Flat pattern length & width in custom properties

Hi all,

Attached is a sheet metal part that we need to make.

When I get the flat pattern and do a measure of the length it comes out as 865.75mm, which is correct.

The width is 500mm which is the extrude.

We would then cut a plate to this size and bend to get finished shape

What I would like to do is have this length & Width now populate the Length / Width box in my custom properties.

I have these custom property boxes set up so they automatically populate with the 1st two dimensions I use to do the 1st sketch I make, (length & width which is usually the finished size of an item).

This then automatically fills in information on my drawings.

However in sheet metal the 1st two dimensions are not the finished size of the plate, I need the unfolded length of the plate

I am guessing that I would need to use maybe the bounding box function to get this length & width.

Does any one have any suggestions on how I can automatically have the length & width fill in these custom properties boxes.

Thanks

Mark (SolidWorks 2012 sp5)

SolidworksSheet Metal