You should be able to link your dimension to the BOM column
Thanks for your reply John but what I mean is how might I get the length, width and thickness to drive the specific columns/properties. For example if I give a dimension of 100mm to a part which is 80mm wide how might solidworks know that the largest of the 2 dimensions is the length? is it possible does anyone know
This is how I do something similar but for populating drawing info.
In the custom property box I have a list of different properties.
These include length, width and thickness.
When doing the 1st sketch the 1st dimension I use is always the length and the 2nd dimension is always the width.
The thickness is linked to the extrude.
These then automatically fill in in the custom properties list, these are then linked to the drawing.
You could set something up to a BOM, by linking the BOM columns to custom properties 'Length', 'Width' and 'thickness'.
Mark (SolidWorks 2015 sp1)