I have gone through my Toolbox and filled in the column for "Part Number" where needed.  My BOM template has a field that uses the custom property "Part Number":

IF(`PURCHASE`=1;`VENDOR`{}": "{}`VENDORNO`;`PART NUMBER`)

Unfortunately the Toolbox "Part Number" field is different than the custom property field labeled "Part Number".  If I set a BOM column to "Part Number" it will recognize both the custom property "Part Number" of my parts and the field "Part Number" of my Toolbox components (right column in picture). When I link the BOM column to the custom property "Part Number", it only recognizes my part properties and not those of the Toolbox components (left column in picture).

Anyone know a workaround for this issue?  I want to use my equation listed above yet keep the part numbers for Toolbox components when used.