If you have the flat length as a custom property, you can pass that information using Get4 http://help.solidworks.com/2017/english/api/sldworksapi/solidworks.interop.sldworks~solidworks.interop.sldworks.icustompropertymanager~get4.html
bool = swCustProp.Get4("Property", False, val, valout)
Create an Excel Object:
Set xlApp = CreateObject("Excel.Application")
Set xlBook = xlApp.Workbooks.Open("File Location")
Set xlSheet = xlBook.Sheets("Sheet")
xlSheet.Cells(2, 1).value = val
Now the last line you could change to find the next open row etc.
Thank you, this sounds like it will work for what I need. I will look further into this weekend.